A NAND flash memory, including a memory cell array, a row decoder, and a sense amplifier. In a read operation, a p-type semiconductor substrate is set at a ground potential, a bit line is charged to a first voltage, a source line, a n-type well and a p-type well are charged to a second voltage, which lies between a ground potential and a first voltage, and in a block not selected by the row decoder, a drain-side select gate line and the source-side select gate line are charged to a third voltage, which is higher than the ground potential and is equal to or lower than the second voltage.