To improve the sealing properties and durability of the rotary valve of a rotary fluid machinery in simple structure.

The rotary valve 61 to control suction and discharge of a working medium in and from a rotor 27 is provided with a valve plate 63 on the fixed side sliding over a slide surface 68 and a valve plate 64 on the moving side. The valve plate 63 on the fixed side made of carbon or ceramics is shrinkage-fitted in a manner to be fitted in the inner periphery of a rotary valve body 62 made of stainless steel and end parts 62f and 62g of steam passages P1 and P7 protruding from the rotary valve body 62 are closely fitted in steam passages P2 and P6 formed in the valve plate 63 on the fixed side. The valve plate 63 on the fixed side is whirl-stopped by the end parts 62f and 62g of the steam passages P1 and P7 and besides during a hot time, the end parts 62f and 62g being high in a thermal expansion coefficient are thermally expanded and leakage of steam can be reliably prevented.