The present invention is directed to increase noise immunity and largely improve the reliability of a memory device by controlling input/output buffers in accordance with a noise state of input/output signals. When a user data read-transfer request is received from a host, a controller checks the presence or absence of an error in read CRC data. When there is an error in the CRC data due to the influence of noise and the like, a data transfer control unit outputs a control signal to an I/O buffer switching unit to switch I/O buffers to a Schmitt input. If there is no error in the CRC data, the controller transfers user data to the host. When a re-transfer request is sent from the host after the transfer, the controller determines that the data transferred to the host was influenced by noise or the like and the data transfer control unit performs the control of the I/O buffer switching unit to decrease the drivability of the output buffer, thereby reducing noise.