The drive part for converting the revolution movement to the wobble movement is composed of the shaft for transmitting the drive force from outside, the swash plate rotated by the shaft and the wobble plate for converting the revolution movement of the swash plate to the wobble movement. Plural pistons are reciprocated in responsive to the wobble movement of the wobble plate. The crank room containing the swash plate, the wobble plate and the piston is separated into the fuel room and the drive room by the bellows. The bearings for transmitting the drive force between the shaft in the drive room and the swash plate, and the bearing for transmitting the drive force between the swash plate and the wobble plate are placed inside the drive room in order to lubricate the bearings. By arranging plural pistons inside the fuel room, the fuel is forced to be taken in and discharged by the reciprocate movement of the individual pistons.