A step motor is composed of a rotor, first and second stators, and a
magnetic member. The rotor is rotatably supported and comprised of a
magnet having magnetic poles magnetized in four angular sections. The
first stator has a pair of counter poles disposed in opposed relation to
the magnet and a coil wound around the first stator. The second stator has
another pair of counter poles disposed in opposed relation to the magnet
and another coil wound around the second stator. The second stator is
opposite to the first stator with respect to the rotor such that the
counter poles of the first and second stators surround the rotor to
stepwise rotate the rotor in response to electric pulses applied to the
coils of the first and second stators. The magnetic member has a pair of
interpoles positioned in a middle of the first and second stators in
opposed relation to the rotor such as to stabilize a rest position of the
rotor, which is held when the electric pulse is not applied to the coils.
