Technical problems of this invention is to create an injection molding device and an injection molding process for a test tube shaped preform, that can laminate a colored layer at certain positions of a wall of the reform with a certain thickness in a manner of a high degree of accuracy.A feature associated with the injection molding device to solve these problem comprising a nozzle section, in which a molten main resin and a molten second resin are join together to form a joined resin mass, the nozzle section comprising: an outer flow channel through which the main resin flows, an inner flow channel through which the second resin flows, a cylindrical column-shaped joined flow channel where the second resin from the inner flow channel joins the main resin from the outer flow channel, a first confluence disposed at a point where the main resin from the outer flow channel flows into the joined flow channel, a second confluence disposed at a point where the second resin flows into the joined flow channel wherein the first confluence is located downstream of the second confluence with a predetermined space left in between, and a cylindrical shutoff pin inserted slidably in the joined flow channel, wherein this shutoff pin is capable of shutting off or opening either or both of the first confluence and/or the second confluence, depending on the sliding position.