A fuel tank cap body unit includes a fuel pump portion which is integrated with a fuel filter portion to form a filter-equipped pump. The filter-equipped pump is fixedly contained in a rotary tank having a flat base with which the base of the fuel tank is brought into contact. A fuel tank cap body through which a fuel discharge flow channel portion is passed, is provided. The fuel tank cap body includes a rotary-tank mounting wall, which can be made flexibly movable by a flexible mechanism, and can accommodate the rotary tank and the filter-equipped pump.