Abstract: In a hot-runner plastic injection system, part of a resin passage connecting the nozzle of an injection molding machine and cavities of a mold adjacent to each of the cavities is formed of a tubular member of material which can be heated by high frequency induction heating. High frequency induction heating windings are wound around the tubular members and are connected to a high frequency power source in series with each other. There is provided a temperature controller for controlling the temperature of the tubular members by controlling the power to be supplied to the heating windings.