To provide a fuel battery power generation system and a valve for controlling gas, which advantageously suppress the vibrations of the movable valve body.

The valve 1 for controlling the gas, which has components comprising a member 3 for receiving pressure; a path 61 on a first side; a secondary side path 71 on a second side through which the gas is discharged via a first room 21; a throttle aperture variable mechanism 4, which has a throttle hole 40, an elastic materials 8 for a movable valve body 41 to energize the movable valve body 41 in a direction (arrow in the direction of Y2), to close a throttle hole 40, and the movable valve body 41 for opening and closing the hole 40; elastic materials 7 for pressure receiving member to energize the part 3 in the direction of increasing the aperture L for the throttle aperture variable mechanism 4; and resistant materials 200, wherein the resistant materials 200 exhibit resistance with respect to the movable valve body 41, when the movable body 41 operates in the direction to close the throttle hole.