To facilitate installation of a mirror supporting frame onto one side face of a sun visor main body.

In a cavity constructed of die faces of a pair of molding dies 21, 22, a sun visor main body 2 is formed of a thermoplastic synthetic resin material 26 by means of air blowing. In this process, a mirror holding frame 3 is previously positioned and held on the die face of one molding die 21, and the mirror holding frame 3 is buried and fixed on one side face of the sun visor main body 2 at the same time when the sun visor main body 2 is molded by means of blow molding.