Memory cell regions as units of erasing operation are sectors S, and units of reading operation and/or writing operation are blocks B0 to B3 in a sector, in which a block address BA for selecting one of blocks B0 to B3 is held in block address buffer (BAB) 3. Holding operation is executed prior to reading or writing operation, and hence in subsequent reading operation or writing operation, re-input is not needed. Depending on the held block address BA, any one of selection signals YDn (n=0 to 3) is selected, and any one block is selected depending on the selection signal YDn. This state is maintained until the block address BA held in the block address buffer (BAB) 3 is rewritten, and therefore it is not required to enter or decode the block address BA on every occasion of reading and/or writing operation, so that the access operation can be executed promptly and at low current consumption.