Provided is a method for manufacturing a fiber reinforced resin molded article capable of effectively reducing the occurrence of a preform with poor resin impregnation, and such a manufacturing device thereof. After it is detected that a predetermined amount (the same amount) of resin has been individually poured into a plurality of cavities provided in a mold, the fiber layers of preforms are impregnated (compressively filled) with resin. Pressure sensors for detecting a resin injection amount are used. When closing runners, a small gap is formed in the runners.