A fluid machine (10) includes a closed casing (11) in which an oil reservoir (16) for holding oil is formed in a bottom part. Disposed in the closed casing (11) are: a main compression mechanism (3), for compressing a working fluid, to which the oil held the oil reservoir (16) is supplied; a rotary electric motor (8) disposed above the oil reservoir (16) in the closed casing (11); a main compressor shaft (38) for coupling the main compression mechanism (3) and the rotary electric motor (8) to each other; a power recovery mechanism (5) for recovering motive power from the working fluid by performing a suction process for drawing the working fluid and a discharge process for discharging the drawn working fluid; a sub compression mechanism (2), which is driven by the power recovery mechanism(5), for compressing the working fluid and discharging the working fluid to the main compression mechanism (3) side; and a power recovery shaft (12) for coupling the power recovery mechanism (5) and the sub compression mechanism (2) to each other.