PURPOSE: To improve the appearance of a motor bicycle by introducing a bleed tube into a sub-tank through the bottom plate of a main tank in a system provided with the breather tube connecting the main tank to the sub-tank.

CONSTITUTION: A fuel tank 4 is divided into a main tank 7 arranged on a pair of the left and right frame pipes 1a constituting the upper portion of a car body and provided with a front filler port 5 and a rear fuel outlet 6 and a sub-tank 9 provided with a fuel inlet 8 connected to the fuel outlet 6. A breather pipe 14 connecting the sub-tank 9 to the main tank 7 is arranged at the intermediate section between both frames 1a on a lower bottom plate 7a constituting said main tank 7. This breather pipe 14 extends into the main tank 7 after penetrating the bottom plate 7b in the up-and-down direction. Also, the fuel outlet 6 is arranged in the same way as the breather pipe 14.