A heat-radiating light source including a heat-radiating layer and a substrate laminated thereon for heating the heat-radiating layer is disclosed. A heat-radiating layer and a substrate for heating the heat-radiating layer are laminated. In the heat-radiating layer, there are provided a radiation control portion and a radiating transparent oxide layer, the radiation control portion having an MIM lamination portion including a pair of platinum layers juxtaposed along lamination direction and a resonating transparent oxide layer formed of a transparent oxide and disposed between the pair of platinum layers, the radiation control portion and the radiating transparent oxide layer are laminated with the radiation control portion and the radiating transparent oxide layer are disposed closer to the substrate in this order. The resonating transparent oxide layer R has a thickness providing a resonance wavelength equal to or smaller than 4 μm.