The purpose of the present invention is to provide a metal-resin composite body (1) which exhibits excellent high-frequency signal transmission characteristics and which exhibits excellent adhesive properties between a synthetic resin part (2) and a base part (3). The present invention is a metal-resin composite body comprising a metal base part and a synthetic resin part which is bonded to at least a part of the outer surface of the base part and which has a fluororesin as a main component, wherein the metal-resin composite body is characterized in that a silane coupling agent which has a functional group having a N atom or a S atom is present near the interface between the base part and the synthetic resin part. The silane coupling agent is preferably an aminoalkoxysilane, a ureidoalkoxysilane, a mercaptoalkoxysilane, a sulfide alkoxysilane or a derivative of these. The silane coupling agent is preferably an aminoalkoxysilane into which a modifying group is introduced. The modifying group should be a phenyl group. The fluororesin is preferably FEP, PFA, PTFE or TFE/PDD.