Abstract: A check valve for controlling a pneumatic threaded fastener-setting tool comprises a hollow cylinder housing connected between the tool and a pneumatic source for transmitting the air pressure therethrough, a retaining ring, a stopper member, a guider member, a slide and the springs sequentially disposed inside the housing. An actuator rod inserted into the tool pushes the slide moving inward for permitting the stopper member to close an air duct in order to interrupt the air fluid from going through thus to stop a shank of the tool from further extracting movement.