A light-emitting element mounting substrate is provided. The light-emitting element mounting substrate includes an insulating base plate comprising a first surface, a second surface facing the first surface, and a plurality of pad regions disposed on the first surface in an m-by-n matrix form, each of m and n being a natural number; a first conductive pad that is disposed in one of the plurality of pad regions and is in contact with the insulating base plate; a second conductive pad that is disposed in another one of the plurality of pad regions apart from the first conductive pad and is in contact with the insulating base plate; a first through hole disposed at a position corresponding to the first conductive pad to penetrate the insulating base plate; a second through hole that is disposed at a position corresponding to the second conductive pad to penetrate the insulating base plate and is spaced apart from the first through hole; a first through conduit filling the first through hole and being in contact with the first conductive pad; and a second through conduit filling the second through hole and being in contact with the second conductive pad.