The inside of a cylindrical body is divided into two parts, that is, a first and a second chamber, and in a piston body, a first ventilation hole and a first ventilation path of a pushing portion are formed so as to communicate with the first chamber and a second ventilation hole and a second ventilation path of the pushing portion are formed to communicate with the second chamber, and a spring for returning the piston body to its original position is provided. By pressing the pushing portion while closing the first ventilation port so as to advance the piston body, air is supplied through a syringe port on the first chamber, while by pressing the pushing portion while closing the second ventilation port, air is supplied through the syringe port on the second chamber, and by releasing the pushing operation, the piston body automatically returns to the original position.
