A nailing machine comprising: a striking mechanism including a piston integrally coupled with a driver for striking a nail and a cylinder slidably accomodating the piston; a housing accommodating the striking mechanism and attached with a nose portion for slidably guiding the driver at a front end thereof; a start valve for driving the striking mechanism by supplying compressed air into the cylinder and returning the striking mechanism to an initial position by exhausting the compressed air in the cylinder; a trigger lever operated by a finger; a contact arm operated by bringing the nose portion into contact with a work; a contact lever including an axially supporting portion on one end side of the contact lever which is axially supported pivotably around a rotating shaft and an operating end on the other end of the contact lever which is arranged to be opposed to an upper end of the contact arm, and the contact lever is operated to pivot by operating the trigger lever and the contact arm; a valve stem provided at the start valve and operated by the contact lever; and a switch operating member (40, 51) provided at a front end portion of the contact arm and configured to engage with said operating end of the contact lever and to set a single striking mode and a continuous striking mode; characterized by a pivot restricting mechanism (44, 54) configured to engage with a middle portion of the contact lever between said axially supporting portion and said operating end and to restrict the contact lever from being pivoted, so that the valve stem maintains an ON state of the start valve, when the switch operating member (40, 51) sets the single striking mode. a striking mechanism including a piston integrally coupled with a driver for striking a nail and a cylinder slidably accomodating the piston; a housing accommodating the striking mechanism and attached with a nose portion for slidably guiding the driver at a front end thereof; a start valve for driving the striking mechanism by supplying compressed air into the cylinder and returning the striking mechanism to an initial position by exhausting the compressed air in the cylinder; a trigger lever operated by a finger; a contact arm operated by bringing the nose portion into contact with a work; a contact lever including an axially supporting portion on one end side of the contact lever which is axially supported pivotably around a rotating shaft and an operating end on the other end of the contact lever which is arranged to be opposed to an upper end of the contact arm, and the contact lever is operated to pivot by operating the trigger lever and the contact arm; a valve stem provided at the start valve and operated by the contact lever; and a switch operating member (40, 51) provided at a front end portion of the contact arm and configured to engage with said operating end of the contact lever and to set a single striking mode and a continuous striking mode; characterized by a pivot restricting mechanism (44, 54) configured to engage with a middle portion of the contact lever between said axially supporting portion and said operating end and to restrict the contact lever from being pivoted, so that the valve stem maintains an ON state of the start valve, when the switch operating member (40, 51) sets the single striking mode.