A light source unit includes a plurality of LED elements disposed on a plurality of band-shaped wirings on a substrate. The LED elements on one band-shaped wiring are electrically connected by wires to an adjacent band-shaped wiring. The LED elements are disposed on the substrate in a staggered arrangement as a whole. The LED elements can be densely disposed without poor connection occurring in the wires connected to the band-shaped wirings, and effective cooling can be carried out without impeding the dissipation of heat from the LED elements. One or more damming channels are formed between each two adjacent LED elements on each band-shaped wiring. A non-effusion region is formed, into which no solder flows, between each two adjacent LED elements. The wires are connected to the non-effusion regions.