A semiconductor storage device of an embodiment includes a control circuit configured to execute a writing sequence in which a loop including a program operation that writes data to memory cells and a program verify operation that verifies the data written in the memory cells is repeated a plurality of times by increasing a program voltage by a predetermined step-up voltage each time, the control circuit being capable of executing reading verify that verifies the data written in the memory cells in the writing sequence, and the control circuit detects characteristic variation of a characteristic that causes disturbance, and determines whether to perform the reading verify based on a result of the detection.