External storage device and memory access control method thereof

A storage device, including: a non-volatile semiconductor memory which is electrically erasable; a system interface coupled with an external host system; and a controller reading data from the non-volatile semiconductor memory and transmitting data to the host system via the system interface in response to a read command received by the system interface from the host system; and wherein the controller starts reading (N+n)th sector data from the non-volatile semiconductor memory, while the controller transmits Nth sector data that has been read from the non-volatile semiconductor memory to the host system via the system interface, in response to the read command for successive sector data.