To reduce the depth of a pump acting chamber, and form a diaphragm fuel pump in a compact size by inserting each cylindrical projection formed integratedly with the bulk head of a pump cabinet made of thermoplastic resin into opening holes arranged on intake/discharging side check valves, caulking the end part of the projection by means of heat, and fixing the check valves to a bulk head.

Each cylindrical projection 14 which is enabled to deforme by heating and push-pressing is formed on the bulk head 4 of a pump cabinet 1 formed of thermoplastic resin integratedly with the bulk head 4. After the projections 14 are inserted into inserting hole arranged on intake/discharging side check valves 5, 7, end surfaces of the projection 14 are heated and push- pressed by a heated trowel 15, they are caulked by heat, and then the check valves 5, 7 are fixed to a bulk head 4. The thickness of the end part which is heating-caulked and whose diameter is enlarged in the projection 14 is formed lower than the height of the head of a screw member or the head of a gromet. It is thus possible to make reduce the depth (d) of the pump operating chamber 9, and form a diaphragm fuel pump in a compact size.