Abstract: A joining method includes punching respective laminated plate materials by a rivet shaft portion of a SPR, forming a crimp portion at the front end of the rivet shaft portion, and fastening and joining the laminated plate materials between the rivet head portion and the crimp portion. Washers are laid on and brought into contact with respective opposite surfaces relative to joining surfaces of the laminated plate materials, the washers each having an inner hole through which the rivet shaft portion is allowed to pass, the washers are used as jigs at the time of the punching, the punching by means of the rivet shaft portion is performed along the inner holes of the washers, and the joining is performed so that the washers left between the rivet head and the crimp portion and the opposite surfaces.