This invention relates to a method for manufacturing a large FRP member including: disposing a preform containing a reinforcing fiber on a surface of a molding die; covering a molding portion with a bagging material or a mold and providing a suction port and a resin injection port for sealing; evacuating the molding portion through the suction port; heating the molding portion; injecting a thermosetting resin from the resin injection port for impregnating the reinforcing fiber with the resin while a temperature Tm of the molding die and a temperature Tv of the bagging material or the mold are both set to room temperature or more, and a difference .DELTA.T in temperature between the Tm and the Tv is set to 10.degree. C. or less; and curing the resin by maintaining the molding portion at a predetermined temperature Tpc which is equal to or more than room temperature.