To effectively utilize fuel vapor from a fuel tank as energy without affecting operability of an internal combustion engine and atmosphere.

In this fuel vapor processing device for vehicle, fuel vapor generated in a fuel tank 1 is adsorbed by a canister 2, and the fuel vapor adsorbed by the canister 2 is desorbed to flow into a fuel vapor reforming device 3. The fuel vapor consisting of hydrocarbon and oxygen in the air are reformed, and transformed into hydrogen and carbon dioxide in the fuel vapor reforming device 3. The hydrogen from the fuel vapor reforming device 3 and the oxygen in the air transformed into electrical energy and water by an alkaline fuel cell 4. The transformed carbon dioxide and water are discharged to atmosphere and the electrical energy is stored in a battery 5.