Abstract: Disclosed is a method for the injection molding of a resin to produce a shaped resin article having a thick portion biasedly, wherein an excess filling of the cavity of a mold is effected to form a molten resin mass having opposite, first and second surfaces respectively facing opposite, first and second inner walls of the mold cavity, the mold having a specific structure in which a gas-release passage is formed in association with the mold cavity and with a mating surface of the mold, which gas-release passage has an inner opening in an inner wall surface of the mold cavity and communicates with the outside of the mold, and a pressurized gas is introduced into the mold cavity on a side of the first surface of the molten resin mass, thereby forming a closed space which is filled with the pressurized gas and separated from the gas-release passage through the molten resin mass, so that the pressurized gas filled in the closed space urges the second surface of the molten resin mass to be pressed against the seco