Abstract: A fluid machine including a rotating shaft that extends parallel to a power generation shaft of a power generation unit, and that has an end coupled to the power generation shaft; a multiple rotors that are provided on the rotating shaft so as to be able to rotate in a circumferential direction of the rotating shaft, and that are arranged so as to be spaced in a rotational axis direction parallel to the axis of the rotating shaft; and a differential mechanism that is provided between a pair of rotors lying adjacent to each other in the rotational axis direction, and that combines the rotational force from each of the pair of rotors and transmits the rotational force to the rotating shaft.