To provide a joining method which enables two members to be joined together with sufficient joining strength by driving first and second fixing materials from one-side surfaces of the two members.

In this member joining method, the first fixing material 20 is obliquely driven toward the other member (lateral core material 11) from a surface (panel mounting surface 10a) of the one member (longitudinal core material 12); concurrently with that, the second fixing material 30 is obliquely driven toward the one member from a surface of the other member; and the first and second fixing materials 20 and 30 penetrate the one member and the other member in such a manner that a joint surface 10b serves as a boundary, respectively, so that the members can be joined together.