PURPOSE: To provide a built-in gas powered surgical device for driving a fastener in the organ of a human body by providing a pneumatic device having a pneumatic actuator disposed in a frame and operating a surgical fastener firing means with the pneumatic device. CONSTITUTION: An anvil member 56 includes a long housing attached to be moved between an open position and a closed position, a means for moving the anvil member 56 between the open position and the closed position, a discharging means for discharging a surgical fastener from a cartridge assembly 58, the discharged fastener being engaged with a fastener forming surface, and a sealing means for preventing the dispersion of gas in a frame 52. It further includes a pneumatic device disposed in the frame 52 and having a pneumatic actuator mechanism related to a built-in pressurized gas supply source and a gas supply source, and this pneumatic device operates the surgical fastener discharging means.