PURPOSE: To reduce ineffective fuel that cannot be utilized by installing a fuel pump detachably on a pump support member fixed to the bottom plate of a fuel tank.

CONSTITUTION: A fuel pump 14 is installed directly to three columns 13 which are spot-welded on the upper surface of a sub-tank 12 welded to a lower tank 11b of a fuel tank 11. Therefore, the clearance between a filter 18 and a sub- tank 12 can be reduced. Also, because a fuel pump 14 is deformed similarly when the lower tank 11b and sub-tank 12 are deformed elastically by impact from the outside, the fuel pump 14 will return to the original position if the lower tank 11b, etc., returns back to the original position. Therefor, any problem will not occur. Also, even if the internal pressure of the tank varies according to a variation in fuel amount, and also the distance between the upper tank 11a of the fuel tank 11 and the lower tank 11b varies, a positional relation among the fuel tank 14, lower tank 11b, and sub-tank 12 does not vary, and the sucking capacity of the fuel pump 14 is kept unchanged.