Disclosed is an injection molding device and process for a test tube shaped preform, that can laminate a colored layer at certain positions with a certain thickness accurately. Included is a nozzle section, in which a molten main resin and second resin are joined together to form a joined resin mass, the nozzle section including: an outer flow channel through which the main resin flows, an inner flow channel through which the second resin flows, a cylindrical column-shaped flow channel where the second resin joins the main resin, a first confluence where the main resin flows into the joined flow channel, a second confluence where the second resin flows into the joined flow channel wherein the first confluence is downstream of the second confluence, and a cylindrical shutoff pin inserted in the joined flow channel to open or close one or both the first and second confluences.