ROTARY FLUID MACHINE

A rotary fluid machine is provided that includes a rotor rotatably housed within a casing, a hollow rotating shaft (113) that rotates integrally with the rotor, and a fixed shaft (102) that is relatively rotatably fitted into the inner periphery of the rotating shaft (113); wherein the fixed shaft (102) is floatingly supported in the casing via a fixed shaft support spring (95) having an alignment action. When rotational runout of the rotor is transmitted to the fixed shaft (102) via the rotating shaft (113), the alignment action of the fixed shaft support spring (95) suppresses the rotational runout of the rotor, and any increase in the frictional resistance in a sliding section between the rotating shaft (113) and the fixed shaft (102) and the occurrence of abnormal wear can be prevented effectively, and the leakage of steam from a rotary valve (V) provided on the sliding surfaces of the rotating shaft (113) and the fixed shaft (102) can be reduced.