A NAND flash memory having a memory cell array formed of a plurality of blocks including memory cell transistors arranged in a matrix form. The NAND flash memory has a first bit line; a first sense amplifier connected to the first bit line, the first sense amplifier sensing or controlling a potential on the first bit line; a second bit line; and a second sense amplifier connected to the second bit line to sense or control a potential on the second bit line. The NAND flash memory has a first drain side selection gate line; a second drain side selection gate line; a third drain side selection gate line; a fourth drain side selection gate line; a first source side selection gate line; and a second source side selection gate line. The NAND flash memory has a first block; a second block; and a decoder which turns on one of the first and third drain side selection MOS transistors and turns off the other, and which turns on one of the third and fourth drain side selection MOS transistors and turns off the other.