To provide a novel drive mechanism for a shift member to shift a passage, in a passage switching device for a working medium.

This rotation drive mechanism 30 interconnects a valve element 20 and a drive source through a transmission mechanism 6 and this transmission mechanism 6 transmits rotation in a state to make non-contact with each other through a drive element 6A consisting of a permanent magnet 61 and a passive element 6B formed of a magnetic substance 63. Further, a casing 10 is formed such that the passive element 6B is contained in a state to be hermetically closed at an internal part and a portion extending from the drive element 6A to a drive source is situated outside a hermetically closed range in the casing 10. The rotation drive mechanism 30 is provided with a reduction mechanism 3 is formed that a gear train 34 to switch rotation of a valve element 20 by reducing rotating from a drive element 6A is juxtaposed between the passive element 6B and the valve element 20. This reduction mechanism 31 is contained in a hermetically closed state in a casing 10 togetherwith the passive element 6B.