PURPOSE: To manufacture the composite molded body in a complicated form efficiently by molding a substrate layer, an intermediate material layer and a skin material layer separately and later by putting them into one body.

CONSTITUTION: Mold clamping is conducted with an auxiliary mold 7 being put intermediately between the 1st mold 5 and the 2nd mold 6 and a slight vacuum pipe 8 and a slight pipe 9 for extraction of air are made to advance into a concave part formed in the mold 7 through the intermediary of plates 81 and 91. Thereafter foaming resin beads 1' is injected from an injection pipe 62 into a cavity between the molds 7 and 6, steam is introduced from a steam jetting port 63 to make the beads 1' foam, and thereby the substrate layer 1 is formed and cooled later. Next, the molds being opened with the substrate layer 1 being held on the molding surface of the mold 6, the mold 7 is removed, a sheet 2 for the intermediate material layer and a sheet 3 for the skin material layer both of which are softened beforehand are inserted between the molds 5 and 6, the sheet 2 is closely fitted on the substrate layer 1 by exhausting air inside a chamber 64 by means of a vacuum pipe 67 and further the sheet 3 is closely fitted on the mold 5 by exhausting air in a chamber 53 by means of a vacuum pipe 54. Thereafter the molds 5 and 6 are clamped and thereby the sheets 2 and 3 and the substrate layer 1 are bonded together.