A scanner repeats a threshold voltage correcting process over a plurality of horizontal periods prior to the sampling of a signal potential to hold a voltage corresponding to the threshold voltage of a driving transistor reliably in a retentive capacitor. Each signal line is associated with a pair of switches, one for supplying the signal potential to the signal line and the other for connecting, to the signal line, a common line for supplying a reference potential. A signal selector turns on and off the switches in each horizontal period in timed relation to a line sequential mode to switch between the signal potential and the reference potential and selectively supply the signal potential and the reference potential to the signal line of each column.