To prevent degradation of magnetic force to a driven magnet of a driving magnet, even if applied to a magnetic coupling which transmits the rotation of a power turbine to a reduction gear, and to normally transmit a drive force, for example, in a waste heat recovery power generation device constituting a waste heat recovery type ship propelling device arranged for recovering the waste heat of a diesel engine (internal combustion engine) as a ship propelling main machine.

An outside holding ring 101 which exhibits a ring shape in a plane view and is composed of fiber reinforced plastic is attached to the outer peripheral surface of a circumferential wall 82 of an outer yoke 83.