which the springs 30 are fully extended or in its free state so as to generate a desired nozzle touch force which never causes deformation of the stationary mold half 9 even in the mold lockup released section of the injection molding cycle this makes is possible to avoid leakage of the molten resin from a portion at which the mold and the nozzle are joined at the time of the lockup released section of the injection molding cycle being carried out particularly in the case of the hot runner type mold when the injection molding cycle is stopped in response to an operation of a manual switch or supply of a command from the controller 200 for releasing the nozzle touch state the brake 32 is rendered inoperative and then the motor 27 is rotated in the reverse direction to cause the ball nut 29 to retreat thereafter the springs 30 are brought into its fully extended state and then the ball nut 29 urges the projecting wall 15a of the extruder base 15 to thereby retreat the injection unit 3 from its nozzle touch position up to a position where the injection unit 3 is capable of being swiveled as a modification of the aforementioned embodiment an induction motor may be employed as the motor 27 and a timer for setting the distance l2 by which the springs 30 are extended may be employed in place of the switch s2 more specifically a time period required for movement of the dog 36 by the distance of l2 can be calculated because the rotational rate of the induction motor is kept constant and the reduction ratio.