A field winding type synchronous machine has a stator having a stator core to which a stator coil is wound, and a rotor that rotates while facing a peripheral surface of the stator with an electromagnetic gap therebetween. The rotor includes a rotor core having a plurality of main pole portions and interpole portions, main pole windings wound around the main pole portions, interpole windings wound around the interpole portions, and a full-wave rectifier circuit for energizing the field current to the main pole windings. The interpole windings produce the induced current by a magnetic flux generated by a time harmonic current superimposed on a fundamental wave of the stator coil. The electromagnetic gaps between the interpole portions and a circumferential surface of the stator are configured larger than electromagnetic between the main pole portions and the circumferential surface of the stator.