Abstract: A concentric-double-shaft simultaneously rotating apparatus in which a part of the force for driving an inner shaft to rotate is obtained by a device other than a rotation controlled motor to thereby reduce the capacity of the rotation controlled motor to attain reduction in size of the apparatus, increase of stiffness, and so on. The concentric-double-shaft simultaneously rotating apparatus includes at least one permanent magnet which is attached onto an inner circumferential surface of an outer shaft, and a secondary conductor such as a copper pipe, or the like, is provided on an outer circumferential surface of the inner shaft to create an induced current flow.