To reduce a deficiency when an engine is arranged by offseting its position of the center of gravity to the opposite side of the getting on/off port to the center in the width direction of a bus 1, as well as to realize the lower floor of the bus, even though a compressed natural gas is used as the fuel for an engine loaded in the bus.

At the rear end of a bus 1, an engine 5 is arranged to offset its position of the center of gravity to the opposite side of the getting on/off port to the center in the width direction of the bus 1, and cylinders 9 of the compressed natural gas to be the fuel of the engine 5 are provided on a roof 10. In this case, the position of the center of gravity of the whole bodies of the cylinders 9 is offset to the opposite side of the position of the center of gravity of the engine 5, to the center in the width direction of the bus 1.