A member attaching/detaching device not requiring the supply of an external power for extracting a member from a shaft and the preparation of a separate device for shrinkage fitting. The device comprises a ring (3) formed of a non-magnetic metal, a coil (4) for generating magnetic field disposed adjacent to the ring, a first fixing means (6) for maintaining the position relation of the ring (3) to the shaft (1), and a second fixing means (7) for maintaining the position relation of the coil (4) to the member (2). The member (2) is attached to and detached from the shaft (1) by a magnetic repulsion generated between the ring (3) and the coil (4).