A widely applicable and low cost module substrate with a high accuracy, reliability and heat-radiation structure. A light source includes: a heat radiation substrate; an insulating layer formed in some regions in an upper surface of the substrate; a wiring layer having wiring patterns, the wiring layer being arranged on the insulating layer; and a plurality of LED elements connected to the wiring layer. Moreover, the light source includes: a heat radiation substrate; an insulating layer arranged in some regions in an upper surface of the substrate; a wiring layer having wiring patterns, the wiring layer being arranged on the insulating layer; and LED elements connected to the wiring layer, wherein the insulating layer has two layers of a resin layer arranged in the wiring layer side and an adhesive layer arranged in the heat radiation substrate side.