A first swash plate (30) and a second swash plate (40) are disposed on either side of a cylinder block (4), and a plurality of cylinders (6) are disposed in the cylinder block (4). A first piston (8) and a second piston (9) are inserted opposite to each other in each cylinder (6) such that the first piston (8) slides on the first swash plate (30) and the second piston (9) slides on the second swash plate (40). By providing a servo mechanism (33) that tilts the first swash plate (30) and a tilt linking mechanism (40, 70) that tilts the second swash plate (40) in conjunction with the tilting of the first swash plate (30), tilt angles of the two swash plates (30, 40) can be controlled by the single servo mechanism (33).