The present invention relates to a storage device for supporting an iSCSI protocol as an interface with host devices, wherein, in realizing an authentication function of access control following the iSCSI protocol, presence and absence of an authentication of the host device connected under the same port can coexist. In the storage device that can be connected to a plurality of host devices, access information from the host devices is received through the iSCSI port, and the host devices are identified based on the access information and refers to an authentication control table memorized in a shared memory and associating an iSCSI name for specifying the host device in the unit of iSCSI port, with authentication information of the host device (necessity of authentication, user ID/password), to determine the necessity of the authentication to the iSCSI port from the host device. If the authentication is necessary from a result of the determination, the authentication is carried out and accessibility to a memory device is controlled based on the result of the authentication.