A field rotor of a superconducting rotary machine, includes a rotary shaft, a plurality of coil boxes, and a plurality of superconducting coils. The coil boxes extend in a center axis direction of the rotary shaft, have walls defining spaces within the coil boxes, respectively, and are removably fastened to a peripheral surface of the rotary shaft. The superconducting coils are disposed in the spaces of the coil boxes, respectively, and constitute field windings of the superconducting rotary machine.