An injection molding machine is disclosed in which molten resin from an extruder is injected into the cavity of a mold through a nozzle. A runner body disposed between the mold and the extruder has a substantially L-shaped hot runner for supplying the molten resin from the extruder to the mold therethrough. The runner body is pivotably supported by a support assembly and is horizontally slidable relative to the support assembly to accommodate thermal expansion, whereby the nozzle mounted on the runner body can be brought into or out of intimate contact with the mold. To accommodate the thermal expansion of the runner body only toward the extruder, a stopper is provided on the base frame.