According to the embodiments, a first storing unit as a cache, second and third storing units included in a nonvolatile semiconductor memories, and a controller are included, in which the controller includes an organizing unit that increases a resource by organizing data in the nonvolatile semiconductor memories, and an organizing-state notifying unit that, when an organizing-state notification request is input from a host, outputs an organizing state by the organizing unit to the host as an organizing-state notification, thereby improving a command response speed and the writing efficiency.