According to one embodiment, a semiconductor memory device includes a memory which comprises an area accessible from outside and a confidential information area storing confidential information and a set flag. A controller reads the flag from the memory when instructed to erase data in the confidential information area, determines whether the flag is set, erases data in the confidential information area when the flag is clear, and abandons process requested by the data erase instruction when the flag is set. An authenticator uses data in the confidential information area to execute operation for authentication.