In a writing operation, a control circuit raises the voltage of a writing-prohibited bit line among a plurality of bit lines to a first voltage, and thereafter brings the writing-prohibited bit line into a floating state. Then, the control circuit raises the voltage of a writing bit line other than the writing-prohibited bit line to a second voltage. In this way, the control circuit prohibits writing into a memory transistor corresponding to the writing-prohibited bit line. On the other hand, the control circuit executes writing into a memory transistor corresponding to the writing bit line.