To improve the productivity by firmly fixing a mounting bolt for fixing a compressor to a bottom plate by caulking work, and not performing the coating of the bottom plate.

A shaft part 7 of the compressor mounting bolt 5, and a projection 10 mounted on a flange part 9 are respectively inserted into a hole 2 for compressor mounting bolt and a hole 3 for projection respectively formed on the bottom plate 1, a neck part 6 of the compressor mounting bolt 5 is press-fit into the hole 2 for compressor mounting bolt, of the bottom plate 1, and the projection penetrated through the hole 3 for projection, of the bottom plate 1 is pressed from an upper part to be plastically deformed in a state of holding the bottom plate 1, to fix the compressor mounting bolt 5.