A memory includes a sense amplifier connected to one or more of bit lines and configured to sense data stored in the memory cells; and a word line driver configured to control a voltage of one or more of word lines. The memory cells constitute a memory block. The memory cells constitute a memory block being a unit of memory cells on which a data erasing operation is performed. A controller changes an erase condition during the data erasing operation performed on the memory block or a verify condition for a verify check of verifying whether the data has been erased from the memory cells in the memory block, in proportion to a ratio of number of predetermined logical value data to the data in the memory block or the page before the data erasing operation.