There is provided a used-master security system for a printing apparatus that can prohibit the removal of used masters for any type of master and to safely secure used masters by prohibiting the removal of used masters; a used-master security method for a printing apparatus in which the used-master security system of the printing apparatus is used; and a printing apparatus capable of prohibiting the removal of used masters with the used-master security system for a printing apparatus, and having a used-master storage device for storing used-masters provided to the printing apparatus main body and a used-master security device that is capable of prohibiting the removal of used masters inside the used-master storage device.