PURPOSE: To promote the miniaturization and simplification of a pump by setting up two electromagnets as opposed so as to make each one side pole become heteropolarity with each other, and attaching each other polar surface of these two magnets tight to a pump outer case with a magnetic substance part, thereby constituting a closed circuit.

CONSTITUTION: When an ac current is made to flow into an electromagnet 1, a magnetic pole of both N and S poles is alternately produced at both ends of this magnet 1 in synchronizing with a change of the ac current, and thereby an iron core 2 or a magnetic substance is also synchronized with the change the ac current and magnetized, thus each heteropolarity alternately appears in these tips. Thus, an expander 8 reciprocates in both directions as in illustration by dint of attraction and adding force between a tip of the iron core 2 and a permanent magnet 7, and interlocking with this reciprocation, a diaphragm 10 is vibrated right and left. With vibration (displacement) of this diaphragm 10, volume in a pump compression space 14 is varied, thus a fluid such as air and water or the like is sucked or discharged. According to this constitution, a leak of magnetic flux is eliminable, so that powerful output is securable despite compact in size.