POSITION MEASUREMENT APPARATUS

A relative position identifying unit identifies a relative position of a scale to a light receiving unit. An absolute position identifying unit identifies an absolute position of the scale at a timing of execution of a synchronization instruction. A determining unit determines a measurement reference position based on the absolute position at the timing and the relative position at the timing. A current position calculator calculates a current position of the scale based on the measurement reference position and the relative position identified by the relative position identifying unit. A control unit as a synchronization instructing unit executes the synchronization instruction on the absolute position identifying unit and the determining unit.