In a resolver of a motor, a plurality of wires forming a plurality of coils arranged at a resolver stator portion are arranged at a wiring surface which is arranged at a terminal block of a connector portion and extends between an annular shape surface arranged substantially perpendicularly to a central axis at a core back of an insulator and a plurality of terminal pins, and are connected to a control unit via the terminal pins. Each of the wires of the resolver includes a slackened portion formed at a portion thereof between corresponding terminal pins and corresponding coils. The slackened portion is accommodated in a groove portion arranged at the wiring surface of the connector portion in order to minimize the possibility of damaging the wire improving reliability of the connection between the terminal pin and the coil.