diff --git a/roles/host.py b/roles/host.py
index 5bd84f79aca23fdb1797b05c78a6e914b9e40054..cab5836a3d4196d3caca2d135e9be766a037b3d8 100644
--- a/roles/host.py
+++ b/roles/host.py
@@ -147,6 +147,9 @@ class Host(object):
         elif cmd == 'stop':
             self.worker_manager.request_stop()
             return {}
+        elif cmd == 'cancel':
+            self.worker_manager.request_cancel(params)
+            return {'status': 'canceled'}
         elif cmd == 'worker/status':
             self.worker_manager.update_status(params['address'], params['status'])
             return {'status': 'updated'}
@@ -232,6 +235,9 @@ class WorkerManager(object):
 
     def request_stop(self):
         self.broadcast('stop', {})
+    
+    def request_cancel(self, params):
+        self.broadcast('cancel', params)
 
     def broadcast(self, cmd, params, solvers=None):
 
diff --git a/roles/solver.py b/roles/solver.py
index 69427077f56013b9f3e942dc3d6a88528a530a28..2343f35fadd3b2165c38094f5a79d301d817ed85 100644
--- a/roles/solver.py
+++ b/roles/solver.py
@@ -19,9 +19,10 @@ class Solver(object):
         self.solver = importlib.import_module(f"solvers.{config['solver']}")
         self.queue = OrderedDict()
 
+        self.solving = None
+
         self.status = None
 
-        # self.thread = None
         self.thread = threading.Thread(name='solver', target=self.solver_thread, daemon=True)
         self.thread.start()
 
@@ -43,14 +44,15 @@ class Solver(object):
             if len(self.queue) > 0:
                 print("I: Solver started")
                 _, params = self.queue.popitem(last=False)
-                # self.status = f'Running ({len(self.queue)} in queue)'
+                self.solving = params
                 self.set_status(f'Running ({len(self.queue)} in queue)')
-                self.solve(params)
-                # self.status = 'Ready'
+                try:
+                    self.solve(params)
+                except Exception as e:
+                    print("E: An error has occurred in the solver thread")
+                self.solving = None
                 self.set_status('Ready')
             else:
-                # self.status = 'Ready'
-                self.set_status('Ready')
                 time.sleep(0.5)
     
     def solve(self, params):
@@ -65,7 +67,7 @@ class Solver(object):
             solution['elapsed_time'] = elapsed_time
 
         self.submit_solution(params, solution)
-        # self.thread = None
+
         return True
     
     def post(self, path, data):
@@ -94,16 +96,35 @@ class Solver(object):
         print("I: Problem queued")
         _id = params['request_id']
         self.queue[_id] = params
-        # self.status = f'Running ({len(self.queue)} in queue)'
         self.set_status(f'Running ({len(self.queue)} in queue)')
         return {'status': self.status}
         
     def stop_solver(self):
 
-        if self.thread is not None:
-            self.solver.stop()
+        # if self.thread is not None:
+        #     self.solver.stop()
+        self.solver.stop()
         
         return {'status': self.status}
+    
+    def cancel_queue(self, params):
+
+        if 'request_id' in params:
+            request_id = params['request']
+            for k, v in self.queue.items():
+                if k == request_id:
+                    self.queue.pop(k, None)
+            if self.solving['request_id'] == request_id:
+                self.solver.stop()()
+        elif 'problem' in params:
+            problem_name = params['problem']
+            for k, v in self.queue.items():
+                if v['name'] == problem_name:
+                    self.queue.pop(k, None)
+            if self.solving['name'] == problem_name:
+                self.solver.stop()()
+
+        return {'status': 'canceled'}
 
     def call_api(self, method, cmd, params):
         if cmd == 'role':
@@ -112,6 +133,8 @@ class Solver(object):
             return self.start_solver(params)
         elif cmd == 'stop':
             return self.stop_solver()
+        elif cmd == 'cancel':
+            return self.cancel_queue(params)
         elif cmd == 'status':
             return {'status': self.status}
         else:
diff --git a/static/js/adc2019.js b/static/js/adc2019.js
index 369233894841a2cd975519f41a4c17fc237220f1..3708073ddc9556af40e9a2251cd63d2a0462d615 100644
--- a/static/js/adc2019.js
+++ b/static/js/adc2019.js
@@ -30,6 +30,10 @@ class StatusView {
                 _this.start_solver();
             });
             
+            _this.container.find('.cancel-button').click(()=>{
+                _this.cancel_problem();
+            });
+            
             _this.container.find('.save-button').click(()=>{
                 _this.save_solution();
                 _this.fire('refresh');
@@ -112,6 +116,28 @@ class StatusView {
         });
     }
     
+    cancel_problem(){
+        var _this = this;
+
+        var _button = _this.container.find('.cancel-button')
+        _button.html('<span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span><span class="sr-only">Loading...</span>');
+        _button.prop('disabled', 'disabled');
+
+        $.ajax({
+            type: "POST",
+            dataType: "json",
+            url: "/api/cancel",
+            data: JSON.stringify({
+                "problem": _this.problem_key,
+            }),
+            contentType: 'application/json'
+        }).done((d) => {
+            _button.prop('disabled', false);
+            _button.text('Cancel');
+            console.log(d);
+        });
+    }
+    
     // 強制停止
     stop_solver(){
         var _this = this;
diff --git a/templates/part_problem_status.html b/templates/part_problem_status.html
index eca4f65049977b6f026c9d5bcaf3c989be8aa887..64aef0e93943e106c2eaa38cca7820069e755b3d 100644
--- a/templates/part_problem_status.html
+++ b/templates/part_problem_status.html
@@ -1,13 +1,13 @@
 <div>
     <h4 class='inline-heading' id='problem-status-title'>{{problem.name}}</h4>
-    <a href="/viewer#{{problem.name}}" target="_blank">Viewer</a>
     {#% # if localmode %#}
     <button class="btn btn-primary btn-lg start-button" type="button" data-qname="{{problem.name}}">Start</button>
-    <!-- <button class="btn btn-danger btn-lg stop-button" type="button" data-qname="all">Stop</button> -->
+    <button class="btn btn-danger btn-lg cancel-button" type="button" data-qname="{{problem.name}}">Cancel</button>
     <button class="btn btn-info btn-lg save-button" type="button" data-qname="{{problem.name}}">Save</button>
     <button class="btn btn-success btn-lg submit-button" type="button" data-qname="{{problem.name}}">Up</button>
     {#% else %#}
     <!-- [View Only] -->
+    <a class="btn btn-outline-success btn-lg" href="/viewer#{{problem.name}}" role="button" target='_blank'>Viewer</a>
     {#% endif %#}
 </div>