To smoothly execute individual works of supplying, kneading and melting by controlling the temp. in a supplying zone, kneading zone and melting zone to set values in an injection cylinder provided with these three zones.

A groove 10 is arranged between a chip material 4 supplying zone 6 and a kneading zone 7 on the outer peripheral part of the cylinder. Mutual thermal interference between the supplying zone 6 and the kneading zone 7 is prevented by this groove 10 and the temp. of each zone of the injection cylinder 1 can be controlled to the regulated value.