A non-volatile semiconductor memory device achieving low power consumption and erasing method thereof is provided. The flash memory of the present invention includes a memory array formed with NAND type strings. The memory array includes a plurality of global blocks, one global block includes a plurality of blocks, and one block includes a plurality of NAND type strings. When the block of the selected global block is erased and the next block is in adjacent relationship, electric charge accumulated in one of P-wells is discharged to another one of the P-wells, and then the next selected block is erased. Thus, the electric charge is shared between the adjacent P-wells to achieve low power consumption.