In an apparatus which has a kneading part for performing kneading of a material and an injecting part for performing injection of the material for injection molding with the kneaded material and in which the kneading part and the injecting part are connected together, a weighing screw channel portion for weighing the material and a retention screw channel portion that is formed adjacently to the weighing screw channel portion with its channel shape made different and forms a material retention space for retaining the material fed continuously quantitatively from the kneading part are formed on the injection screw shaft. Thereby, the material fed continuously quantitatively from the kneading part can be securely retained in the injecting part where intermittent operation is a performed.
