PURPOSE: To provide a rotational condition detecting device for a step motor whereby a rotational condition of the step motor can be detected without using an exclusive use sensor.

CONSTITUTION: A rotary condition detecting device for a step motor formed so as to drive the step motor 19, provided with a rotor magnetized in multipoles and a stator having multiphase windings 1 to 4 rotated by successively supplying an excitation current to each winding 1 to 2, comprises an induced voltage detecting means (CPU) 33 for detecting induced voltage (f) in the winding 2 with no excitation current supplied and a motor rotary condition judgment means 33 for judging a rotational condition of the step motor by the detected induced voltage.