A method whereby magnetic and nonmagnetic materials can be joined together firmly and having their joining areas freed from embrittlement and with a minimum of deformation is disclosed. Applied to the process of fitting a ring of nonmagnetic material into an annular space formed between an inner and an outer member each made of magnetic material, the method includes bringing an inner and an outer peripheral surface of the ring of nonmagnetic material each into a semi-molten state and bringing the inner and outer peripheral surfaces of the ring of nonmagnetic material into pressure contact with the inner and outer members, respectively, to join the inner and outer peripheral surfaces to the inner and outer members, respectively, by interfacial fusion.