To provide a method for injection molding which does not cause problems such as voids and burning on the occasion of injection molding.

On the occasion of injection molding of olefin resin or norbornane resin by an apparatus for injection, a screw 15 having a compression ratio larger than 2.1 and smaller than 2.5 and a screw cylinder 12 of which a taper angle K of the conical tapered inner wall part 14 near the fore end is larger than 30 degrees and smaller than 90 degrees and of which the part surrounding a region C of a supply part of the screw 15 and a region B of a compression part thereof has the outside diameter G larger than double the inner diameter and smaller than treble the same are used. The part of the screw cylinder 12 being nearest to a water cooling jacket 22 is set at a temperature lower by 40°C or above than the one of the part of the screw cylinder 12 which is set at the maximum temperature.