A controller of a storage device having a user area storing an operating system, the storage device developing the operating system stored in the user area on a host device in accordance with an access from the host device. The controller includes a user authentication routine storage controlling unit that stores a user authentication routine for executing user authentication before startup of the operating system, in a predetermined area inside the user area, and an access controlling unit that permits access to the predetermined area from the host device when the user authentication routine is used, while prohibiting access to the predetermined area from the host device when the user authentication routine is not used.