A semiconductor device according to an embodiment includes a plurality of scan chains each including a retention flip-flop, and a control section configured to perform restoration of data saved in a retention section of each retention flip-flop by reading the data from the retention section and after the data restoration, perform diagnosis of the retention flip-flops by performing comparison to determine whether or not an expected value of an output data string obtained as a result of a scan shift in the plurality of scan chains before the save and a value of an output data string obtained as a result of a scan shift of data in the plurality of scan chains after the restoration.