According to one embodiment, a nonvolatile semiconductor memory includes a semiconductor substrate, a first substrate area in the semiconductor substrate, a first cell unit in the first substrate area, the first cell unit including a first memory cell and a first transistor, and the first transistor having a control terminal connected to a first word line, using the first substrate area as a channel and supplying a read current or a write current to the first memory cell, and a substrate potential setting circuit setting the first substrate area to a first substrate potential when the read current is supplied to the first memory cell, and setting the first substrate area to a second substrate potential different from the first substrate potential when the write current is supplied to the first memory cell.