To provide a rotating fluid machine, preventing the formation of a gap due to a difference in heat expansion coefficients between one of a pair of bearings supporting a rotor at both axial ends on a casing, which supports the axial load of the rotor, and the casing.

The casing 11 is formed of an aluminum material having a greater heat expansion coefficient, and the combined angular bearings 23f, 23r supporting the axial load of the rotor 22, the rotor 22 and a bearing holder 99 are each formed of an iron material having a smaller heat expansion coefficient. Thus, no gap is formed between each of the combined angular bearings 23f, 23r and the bearing holder 99 although there is a difference in heat expansion coefficients between the casing 11 and each of the combined angular bearings 23f, 23r, to avoid the sealing performance degradation of a rotary valve 71 with the axial displacement of the rotor 22 due to the gap.