To provide a hydrogen discharging device capable of discharging hydrogen gas from a fuel cell stack into the atmosphere after diluting it to proper hydrogen concentration below a flammability limit (4%), in a hydrogen discharging device of a vehicle with a fuel cell system mounted.

A first discharge passage 26 connected to the fuel cell stack 4 for discharging oxygen gas and a second discharge passage 36 for discharging hydrogen gas are formed; the second discharge passage is provided with a purge valve 50; a merging part 38 connected with the first discharge passage and a third discharge passage 56 for connecting an atmosphere discharge part 54 are formed by connecting them to each other; and a control means 62 for first stopping the supply of the hydrogen gas to the fuel cell stack in stopping the fuel cell system, then carrying out a slight amount of power generation by the residual hydrogen gas, and thereafter opening and controlling the purge valve is formed.

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