PURPOSE: To prevent solidified resin from remaining in the resin injecting gate at the time of separation of a product by inserting a special sprue lock pin into the resin injecting gate of the sprue unit of a resin former at the time of injection and solidification of resin material into the cavity of the former.

CONSTITUTION: A sprue lock pin 7 on which a groove unit 7A is formed is arranged so that the groove unit 7A is inserted into a resin injecting gate 2B formed on a sprue unit 2. At the time of separation of a formed product, a resin material 20 solidified in the sprue unit 2 is pulled up and it is torn between the groove unit 7A and the internal wall of the injecting gate 2B, and after that, the injecting gate 2B is also detached from a cavity 5 by pulling up an upper mold 1.