A rotary fluid machine comprising a rotor chamber (14) formed in a casing, a rotor (41) rotatably received in rotor chamber (14), a plurality of vane grooves (49) radially formed in the rotor (41), a plurality of vanes (48) slidably supported in the individual vane grooves (49), a vane chamber (75) defined between adjacent vanes (48), and a suction port (90) and an exhaust port (91) for feeding a gas phase working medium to and discharging it from the vane chamber (75). In a region located between the terminal end of the exhaust port (91) and the initial end of the suction port (90) and in which the difference in pressure between adjacent vane chambers (75) increases, a labyrinth (43g) formed in the outer peripheral surface of the rotor (41) prevents the leakage of the gas phase working medium.
