Mirror base

A mirror base according to the present invention secures sufficient flexural strength of a support piece 1B relative to a mount piece 1A thanks to a reinforcing core member 3 buried across the mount piece 1A and the support piece 1B, whereby the mount piece 1A and support piece 1B do not have to be integrally molded of a high-rigidity resin or die casting material, but can be integrally molded of a lightweight, inexpensive resin material. Since the core member 3 is provided with mounting nut portions bordering a mounting surface of the mount piece 1A and integrally molded with the core member, there is no need for a post-process of fixing mounting nut bushes or stud bolts to mounting bosses, for example, by heating and press fitting as needed before.