A light-source driver for a light-source, detachable from an endoscope body includes a first switch, a pilot lamp, a warning lamp, a second switch, and a light switcher. The first switch switches between the On-state and Off-state in connection with the attachment and detachment of the light-source to the endoscope body. The pilot lamp indicates that the illumination light source is energized. The warning lamp indicates that the output voltage of a battery has dropped below a predetermined value. The second switch switches the warning lamp between the On-state and Off-state in connection with the On-state and Off-state of the first switch. The light switcher switches the pilot lamp to the Off-state and enables the second switch when the second switch is set to the On-state and the output voltage has declined to or below the predetermined value.