PURPOSE: To make the captioned pump compact by forming an armature in between a core and a pump chamber, carrying out a suction stroke by means of a solenoid mechanism, and carrying out a return stroke by means of a return spring.

CONSTITUTION: An armature part 13 is provided on a piston shaft 4 in an operating chamber 3 forming a solenoid mechanism together with a core 14 and coils 15. In a suction stroke, an electromagnet M is excited operating the solenoid mechanism and a suction valve 9 is opened to suck in air. In a return stroke, the electromagnet M is not excited and the piston shaft 4 is moved to the right by the action of a return spring 18. Hence, the return spring can be formed small making the whole device compact.