It is an object of the present invention to securely and integrally join a metal and a resin, more particularly, a shaped titanium alloy substrate and a resin composition. A titanium alloy substrate is used that has undergone surface roughening by chemical etching or the like so as to have a ultrafine textured face in which bent, ridge-like protrusions having a width and height of from ten to a few hundred nanometers and a length of from a few to a few hundred microns rise up on the surface at a spacing period of from ten to a few hundred nanometers. A titanium alloy piece 1 with its surface treated is inserted into the cavity of a metallic mold for injection molding 10 and a specific resin composition 4 is injected to obtain an integrated composite 7. The main resin component of the resin composition 4 that is used can be a polyphenylene sulfide resin (PPS) or a polybutylene terephthalate resin (PBT). High injection joining strength is obtained if the resin composition contains, as an auxiliary component, a polyethylene terephthalate resin and/or polyolefin resin in the case of PBT and a polyolefin resin in the case of PPS.