Sealing method

A composite molded body comprising:

• a metallic molded body and a resin molded body sealing the metallic molded body;
• the metallic molded body having a cavity therein;
• the metallic molded body having at least one opening through a joining surface with the resin molded body, the at least one opening through the joining surface is directly connected to the cavity;
• the joining surface of the metallic molded body with the resin molded body is roughened at a periphery of the at least one opening, the roughened joining surface at the periphery of the at least one opening of the metallic molded body having a porous structure in which holes are formed in a range of an average depth from 10 to 70 μm;
• and
• with the resin having been solidified in a state of entering into an interior of the porous structure formed in the joining surface at the periphery of the at least one opening of the metallic molded body, the at least one opening of the metallic molded body is sealed with the resin molded body in the composite molded body.