A metal member (3) is bonded with an adhesive (6) to have a bond strength higher than the basic material strength of the metal member (3). A metal insertion coupling has a socket portion (4) in which an insertion hole (2a) for inserting the end portion of the metal member (3) is formed. The socket portion (4) has a tapered outer surface extending from the opening end to the back side. The tensile strength of the socket portion (4) at the deepest position along the center line of the insertion hole is equal to or higher than the tensile strength of the metal member (3) in the direction of the center line. The insertion hole (2a) has a width 0.2 mm-0.6 mm larger than that of the end portion of the metal member (3). The end portion of the metal member (3) is pressed into the insertion hole (2a), and an adhesive exists densely between the end portion of the metal member (3) and the surface of the insertion hole (2a), by quenching or cold working the end portion of the metal member (3).