SUBSTRATE FOR MOUNTING LIGHT EMITTING ELEMENT, AND LIGHT EMITTING DEVICE

PROBLEM TO BE SOLVED: To provide a substrate for mounting a light emitting element which is an LTCC substrate for mounting a plurality of two wire type light emitting elements so as to electrically connect them in parallel, and a light emitting device using the substrate and having excellent light extraction efficiency and high emission luminance.SOLUTION: The substrate for mounting the light emitting elements has a substrate body made from a sintered body of a glass ceramic composition and having a mounting surface including a mounting part of the light emitting elements, and a wiring conductor layer provided so as to be connected by wire bonding to a pair of electrodes which each of the light emitting elements has on the mounting surface of the substrate body, where the sum of areas of the mounting parts of the plurality of light emitting elements is 10-35% of an area of a mountable region on the mounting surface, and a relative external quantum efficiency is 90 or greater. The relative external quantum efficiency is a value relative to external quantum efficiency set as 100 when a total mounting region obtained by adding a formation part of the wiring conductor layer to the mountable region is covered with a silver reflection film having reflectance of 95%.