In a feed piston and cylinder mechanism for feeding a feed claw that engages with and disengages from connected nails accommodated within a magazine to a nose portion, the feed claw is biased in a feeding direction by a bias member and is retracted in a backward direction by high-pressure combustion gas. A valve is provided in a path which guides the high-pressure combustion gas to the feed piston and cylinder mechanism and communicates the path with the atmosphere. The feed piston and cylinder mechanism is controlled by opening/closing the valve.