To solve the problem that a conventional method of manufacturing a preform for an RTM molding, employing trimming by a cutter or the like after molding the preform in accordance with a cavity of a mold for the RTM molding, causes an uneven deviation to be large to the cavity to decrease the precision of the RTM molding.

The method for manufacturing the FRP preform employs the trimming of the outer peripheral part of a laminate under the condition that a plurality of sheets of reinforcing fiber base materials with interlaminar fixing agent are placed on a bottom mold whose shape forming face has a recessed shape and/or a projected shape and at the same time pinched in the outer peripheral part when or just after the laminated sheet is clamped by the bottom mold and a top mold to make it along the mold.