According to one embodiment, a nonvolatile semiconductor memory device, a controller, an extended function section, and an extension register. The controller controls the nonvolatile semiconductor memory device. The extended function section is controlled by the controller. The extension register which is provided with a certain block length capable of defining an extended function of the extended function section. The controller processes a first command to write header data of a command to operate the extended function section to the extended function section through the extension register, and a second command to read header data of a response from the extended function section through the extension register.