PURPOSE: To provide a position detecting apparatus for moving body which can highly precisely detect the position of window glass, etc., of a power window apparatus, and besides, can set an initial position without complicated adjustment with a simple mechanism at a low cost.

CONSTITUTION: As for the position detecting apparatus 30, a ring gear 46 rotates together with a motor output shaft and a prescribed rotary position is detected by a movable contact point 50 and a fixed contact point 60. In this case, the projected part 66 of a gear base 56 is brought into contact with a contact face 35 of a base plate 34, the difference of loss torque is widened between the gear base and the ring gear 46 and a planetary gear 54 does not rotate unnecessarily. At the time when the output shaft rotates after that, a carrier 56 is released from being held by a wave washer 58 and the rotation of the output shaft is not transmitted to the ring gear 46. Consequently, an initial state is automatically restored by sufficiently rotating the output shaft at the time of assembling.