An illuminating device includes a light emitting element constituted of a light emitting diode, and a light guide plate including a light receiving section provided on a side face and opposed to the light emitting element. The light guide plate emits illuminating light from a first surface. The light receiving section includes a plurality of cylindrical lens surfaces each formed of a concave curved surface oriented such that an axial direction of the curved surface is parallel to a thickness direction of the light guide plate, the cylindrical lens surfaces being aligned in a direction orthogonal to the axial direction. The cylindrical lens surface is formed of an arcuate surface having a curvature radius of 0.5 mm or less, and more preferably 0.2 mm or less.