A ceramic board is formed in an almost rectangular shape and has one side surface of an outer peripheral surface formed as an abutting surface, which is caused to abut on positioning surfaces of a radiating member, and one surface in a vertical direction formed as a device disposing surface on which a semiconductor light emitting device is to be disposed. Predetermined conductive patterns are formed on the ceramic board. A light emitting portion has a semiconductor light emitting device. A pair of positive and negative planar electrode portions are formed on the ceramic board and connected to the semiconductor light emitting device through the conductive patterns. At least a part of the pair of planar electrode portions are set to be exposure regions exposed to the device disposing surface of the ceramic board and the exposure regions are positioned in portions other than a portion linked to the abutting surface in an outer peripheral portion of the device disposing surface.