The present invention provides a composite molded body in which a rubber layer in the form of a thin film is formed on a surface of a resin molded body and a production method therefor. According to an embodiment of the present invention, a liquid composition containing a rubber component such as a rubber latex and a peroxide is applied to a surface of a resin molded body such as a polyamide-based resin having an amino group, causing crosslinking to occur in an uncrosslinked rubber layer and forming a crosslinked rubber layer in the form of a thin film. When a co-crosslinking agent is used in combination, adhesion to the resin molded body can be improved even when the thickness of the crosslinked rubber layer is small.