A scan signal driver includes: a plurality of stages configured to be driven by dividing a first frame period into a display period and a sensing period, and to sequentially output scan signals at the display period, wherein each of the plurality of stages comprises: an output control circuit; and a memory control circuit, wherein the scan driver is configured to: irregularly set a specific stage of the plurality of stages at a display period every frame; control the specific stage to: store a voltage by using the memory control circuit; and output a sensing signal by using the stored voltage at a sensing period, and the memory control circuit includes: a second memory transistor configured to electrically connect an M node with an I node; and a third memory transistor configured to electrically connect the output control circuit with the I node.