A substrate for mounting a light-emitting element includes a base and a dam part. The base includes a front surface and a back surface that are principal surfaces thereof where the front surface includes a mounting part that is capable of mounting a light-emitting element thereon. The dam part is arranged on a peripheral part of the front surface to surround the mounting part. The front surface is inclined relative to the back surface at a predetermined angle. The dam part is provided with an opening part at a site where the front surface is inclined to decrease a thickness of the base, in the peripheral part of the front surface. A site of the dam part where the opening part is provided is inclined relative to the back surface in a direction of the front surface.