This production method for fiber reinforcing members has: a step (1) in which a molten body of thermoplastic resin is formed in a lower mold, a mat-shaped material formed from a reinforcing fiber (B) is placed upon the molten body, an upper mold for pressurizing is closed on the lower mold, pressure is applied thereto and impregnation processing performed, then the resin-impregnated mat-shaped material is cooled and solidified, and a main body section formed from the fiber-reinforcing resin is formed; and a step (2) in which the upper mold for pressurizing is opened, an upper mold for injection molding is closed on the lower mold and an injection molding mold is formed, injection molding is then performed and an additional part is formed, and a fiber reinforcing member having the additional part combined with the main body section is molded.