PURPOSE: To soften impact force and to prevent damage of a spool etc. by providing a speed changing device to a motor that moves a plunger vertically, and when failed to store a medium part in a case, retrying it with slowed operation speed.

CONSTITUTION: A speed changing device is provided to a DC motor that drives a plunger 14 vertically. When unloading a cartridge, a projection 21 of a spool 5 is engaged with an idler key 16 at the tip of the plunger 14 and pulled upward. Sometimes, the engagement is defective to cause failure in pulling up. When retrying at that time, the operation speed of the plunger 14 is slowed down by the speed changing device of the motor. Thus, the impact force to the spool 5 is softened and the damage of the spool 5 etc. can be prevented.