Provided is a method for manufacturing a fiber reinforced resin molded article capable of distributing the pressure without concentration on the vicinity of the resin inlet and so preventing the deformation of a preform, and such a manufacturing device thereof. The method lowers a lower core as a moving core in a lower mold (first mold) (away from a preform) to let resin flow toward the lower mold (first mold). This distributes the pressure concentrated in the vicinity of the resin inlet and prevents deformation of the preform.