PURPOSE: To produce a large vibration by simply varying the number of turns of a coil by forming a three-phase flat coreless armature for eccentric vibration such that the central armature coil has a number of turns larger than those of other armature coils.

CONSTITUTION: Since a central armature coil 3-2 constituting a flat coreless armature 6 for eccentric vibration has a larger number of turns than other armature coils 3-1, 3-3, it produces a higher torque and the weight thereof is heavier than other coils. Since the torque and centrifugal force can be increased in the direction of the center of gravity which contributes most to the vibration, a larger vibration can be obtained as compared with the case where the flat coreless armature 6 for eccentric vibration is rotated. Furthermore, since a commutator board 27 is secured to the lower surface part concentrically to a fixed shaft, a rotating torque is generated continuously in a predetermined direction to produce an eccentric rotation accompanied with a partial circular motion. This constitution can generate a large vibration by simply increasing the number of turns of one armature coil.