A safety lock mechanism mounted at a trigger switch handle of a miter saw to face toward a switch which includes a switch button pivotally mounted at the trigger switch handle to face toward the switch, and a safety lock connected to the switch button and providing an engaging portion and movable between a locking position where the engaging portion engages into the trigger switch handle to lock the switch button to the trigger switch handle and an unlocking position where the engaging portion is disengaged from the trigger switch handle for allowing the switch button to be moved relative to the trigger switch handle to trigger the switch. Thus, the arrangement of the safety lock prevents the user from accidentally forcing the switch button to trigger the switch, enhancing the operational safety of the miter saw.