To improve mountability of a fuel pump inside a sub-tank.

A first grommet is inserted into the outer periphery part PC on one side of a fuel pump P to be fixed and a second grommet 2 is inserted into the outer periphery part on the other side of the fuel pump P to be fixed. A first supporting plate 3 is inserted into the outer periphery part of the first grommet 1 through a first insertion hole to be fixed and a second supporting plate 4 is inserted into the outer periphery part of the second grommet 2 through a second insertion hole to be fixed. A pair of first mounting piece parts of the first supporting plate 3 are inserted into a pair of first mounting grooves through an opening part on the top of a sub-tank 5 to be fixed and a pair of second mounting piece parts of the second supporting plate 4 are inserted into a pair of second mounting grooves through an opening part 5L on the top of the sub-tank 5 to be fixed.