To provide a forward check valve that can prevent the adhesion of a diaphragm and the bottom of a valve chamber even if the valve is low in height, and a fuel cell system having the forward check valve.

In a valve case 130, there are formed, around a flow-in hole 143 on the bottom 141 of the valve chamber 140, a semi-circular protrusion 144 to which the diaphragm 120 abuts on when a valve 150 is released, and a passage for making methanol pass from the inside of the protrusion 144 to the outside. Furthermore, the protrusion 144 is formed into a shape which satisfies a relationship of h>2γSb/Fs. By this arrangement, in the forward check valve 101 in this embodiment, the diaphragm 120 contacts with the protrusion 144 and does not contact with the bottom 141 of the valve chamber 140 at the release of the valve 150, and its lowering amount is regulated. Furthermore, when the diaphragm 120 contacts with the protrusion 144, the methanol passes to the outside of the protrusion 144 via a passage from the inside of the protrusion 144.