To enable a height arranging an opening end of a filler tube to increase, so that oil supply workability can be improved without deterioration of safety at vehicle collision time.

An opening end 3 of a filler tube 2 is set in the vicinity of an opening 8a of a filler base 8. In this way, at oil supply time, fuel bubble coming to rise in the filler tube 2 is prevented from easily leading to a sensor for an auto stop of an oil supply gun, oil supply workability can be improved. At running time, deviation of the filler tube 2 by vibration is absorbed by an elastic seal material 21, and at vehicle collision time, by breaking an easy break part 19 in a bending molded base part of a flange part 18 in a filler cap protector 16, the filler base 8 and the filler tube 2 are separated, and ensuring of safety can be attained.