A fuel cell system includes a supply channel having first channels respectively connected with tanks, and a second channel merged with each of the first channels; first on-off valves of the first channels; a second on-off valve of the second channel; and a controller configured to control opening and closing of the first on-off valves and the second on-off valve. In a state where the second on-off valve is closed, the controller supplies first electric power used for opening the first on-off valve against a first differential pressure to at least one first on-off valve, and supplies second electric power, smaller than the first electric power and used for opening the first on-off valves against a second differential pressure smaller than the first differential pressure, to the first on-off valves other than the at least one first on-off valve.