A display driver used in common for a first screen and a second screen. The display driver includes a data line drive circuit which supplies gray scale voltages to the first and second screens in accordance with display data via data lines in common for the first and second screens, and a scan line drive circuit which supplies scan signals to the first and second screens via scan lines, with the scan lines in the first screen being different from the scan lines in the second screen. The scan line drive circuit scans the second screen in one of a one-line-at-a-time operation and a plural-line-at-a-time operation by using the scan signals every time the scan line drive circuit scans at least one frame of the first screen in a one-line-at-a-time operation by using the scan signals.