Abstract: The present invention relates to a method for molding an agglomerated preform of a fiber-reinforced composite material comprising a resin material as a matrix and reinforcing fibers dispersed therein, into a desired shape. In the molding method, the preform is heated from the interior thereof, whereby the temperature of the entire preform can be raised efficiently and uniformly. If an optional number of holes are formed in the agglomerated preform, rod-like heaters for heating or gas nozzles for the release of heated gas can be inserted into the preform easily through such holes, whereby uniform heating can be effected. Further, by incorporating an appropriate amount of a dielectric loss improver into the preform and thereafter subjecting the preform to high-frequency heating or microwave heating, the preform can be heated efficiently and uniformly in a short time.