Abstract: Disclosed is a technology for eliminating the need for the adjustment of imbalance in an injection molded product and also enabling multi-cavity molding, a method of multi-cavity injection molding including: a dividing step of dividing a molten resin material into a plurality of portions; a resin density adjustment step of adjusting a resin density distribution; and a filling step of filling the molten resin material into a region where the molten resin material is formed into a molded product. The method of multi-cavity injection molding has a configuration containing a combined-use step which includes both a hot runner step and a cold runner step. The combined-use step is dividing the molten resin material from the hot runner to the plurality of cold runners through a spool and a branch runner. A plurality of series of steps from the dividing step to the filling step is concurrently performed in one mold.