In a double drive shaft motor, a stator and a field rotor are arranged at a radially outer side of a magnetic modulation rotor. The stator and the field rotor are arranged in series in an axial direction of the motor. This structure increases an amount of a winding coil of the stator and magnets in the field rotor, and an output torque of the motor. When a field magnetic flux passes through soft magnetic material members in the magnetic modulation rotor, because the generation and the reception of the magnetic flux can occur at a radially same side of the magnetic modulation rotor, this structure cancels an eddy current generated in the soft magnetic members and supporting members made of non-magnetic metal which tightly support the soft magnetic member. This structure provides a reduced axial size of the motor with high performance.