This lighting device (1) is provided with a first light source (L1) and a second light source (L2). The first light source (L1) emits a first light. The second light source (L2) emits a second light. The first light and the second light have substantially the same color temperature but different spectral characteristics. This lighting device (1) is configured such that the first light and the second light are alternately irradiated onto a road sign (2).