A command analyzer 160 determines whether or not a first write command after power-on is issued. A new block reserve determinator 170 determines that a new physical block is reserved, in a case where the command analyzer 160 determines that first writing command after power-on is issued and the physical block corresponding to a logical address at which a host device requests transmit is in a written state. At this time, the semiconductor memory device writes data to the new physical block. Thereby, data written before power disconnection does not been destroyed.