To eliminate a state of forgetting to perform switching operation by switching single driving action and continuous driving action without special switching operation.

A regulating member 15 is disposed near an idler 12 provided at a trigger 10. When the push operation of a contact arm 20 is performed after the pull operation of the trigger 10, the return of the idler 12 is not regulated by the regulating member 15 so as to switch to continuous driving action. When the pull operation of the trigger 10 is performed after the push operation of the contact arm 20, the return of the idler 10 is regulated by the regulating member 15 so as to switch to single driving action.