To simply fill a natural gas supplied from a low pressure gas fuel supply source such as a city gas piping in a high pressure vessel mounted on a vehicle.

A compressor 17 for compressing the supplied low pressure gaseous fuel (natural gas) upto a prescribed pressure is mounted on a vehicle. When the low pressure gas fuel is filled in a high pressure vessel 9, at first an engine 1 is driven, the compressor 17 is driven by the drive force of this engine 1 and the low pressure gas fuel is filled into the high pressure vessel 9 after compressing to the prescribed pressure. By mounting the compressor 17 on the vehicle and driving this compressor 17 by the engine 1, the gas fuel can be filled anywhere without searching CNG service station and at the place where the low pressur gas fuel supply source such as a city gas piping can be ensured.