According to one embodiment, an illuminating device includes a lightguide plate including a curved emitting surface, and an incidence surface including a side edge curved along the emitting surface, a printed circuit board facing the incidence surface, and light sources mounted on the printed circuit board. Each light source includes a light-emitting center, a pair of connection terminals, and a central axis extending through the connection terminals and the light-emitting center. The light sources are arranged along a curved mounting line extending along the curved side edge of the incidence surface on the printed circuit board. The light-emitting centers are located on the mounting line, and the central axes are parallel to each other.