PURPOSE: To provide such a parametric motor that the possibility of cracking of its common core is reduced as much as possible at the time of assembly even when the common core is made of a ferrite and its exciting cores can be easily set to their proper positions.

CONSTITUTION: A surface layer member 13 is mounted on a common core 2 by molding a resin. A cut recessed section 14 is formed at part of the member 13 where projections 3a and 4a of exciting cores 3 and 4 come into contact with. At the time of assembling this parametric motor, the exciting cores 3 and 4 are positioned by putting the projections 3a and 4a in the recessed section 14. In addition, when the common core 4 is put and fixed between the exciting cores 3 and 4, the force acting on the common core 2 is received by the surface layer member 13.