According to one embodiment, a control unit subjects a light-emitting element to constant current control in a dimming degree region shallower than a dimming degree set in advance and subjects the light-emitting element to constant voltage control or constant power control in a dimming degree region deeper than the dimming degree set in advance. When a dimming signal having a deepest dimming degree equivalent to extinction of the light-emitting element is input in a lighting state of the light-emitting element, the control unit gradually reduces an optical output of the light-emitting element from an immediately preceding dimming degree to extinguish the light-emitting element.