PURPOSE: To improve the accuracy with a quick filling thoroughly to tips by injecting a melted resin rotating it on the center of a thin-disc-shaped cavity provided in a telescopic element.

CONSTITUTION: A thin-disc-shaped cavity 6 is provided in a fixed telescopic element 5 and a gate 7 is communicated to the center thereof to feed it 6 with a melted resin. A motor 20 is driven to rotate a mobile telescopic element 15 and the fixed telescopic element 5 integral therewith through a pin 21. A cylinder 8 contacts the fixed telescopic element 5 without rotating. A melted resin is injected into the cavity 6 through the gate 7 from the cylinder 8. The rotation of the telescopic elements 5 and 15 makes the injected resin easy to flow to the tip of the cavity 6 due to a centrifugal force to fill the cavity 6. Then, the melted resin is cooled hard with a refrigerant and then, taken out.