PURPOSE: To improve drive efficiency and reduce weight and to prevent deterioration of a diaphragm during rest.

CONSTITUTION: An electromagnetically-driven air pump comprises a cylindrical magnetic frame 6 around which two exciting coils 7 and 8 are wound so that one pole is formed at two ends and the other pole at a central part; a variation piece 9 wherein a magnetic pole is formed at two ends and a central part is contained in a frame reciprocatively with the flange part 6a of the magnetic frame 6 forming a center; and a pump chamber 1 having a diaphragm 3 connected to one end of the slide piece 9. A magnetic force is exerted on the vibration piece 9 from the two ends of the magnetic frame 6 and the central part thereof.