A fluid machine includes a piston, a valve seat plate, a valve, and a valve retainer that reduces an opening amount of the valve. One end of the valve retainer is fixed with a fastener together with the valve to the valve seat plate. The fastener spans through the one end of the valve retainer and the valve to thereby fasten the one end of the valve retainer and the valve to the valve seat plate. A second end of the valve retainer that is opposite to the one end does not contact the valve seat plate.