A light-emitting element assembly includes a support substrate having a first surface, a second surface facing the first surface, a recessed portion, and a conductive material layer formed over the first surface and the inner surface of the recessed portion, and a light-emitting element. The light-emitting element has a laminated structure including a first compound semiconductor layer, a light-emitting portion, and a second compound semiconductor layer, at least the second compound semiconductor layer and the light-emitting portion constituting a mesa structure. The light-emitting element further includes an insulating layer formed, a second electrode, and a first electrode. The mesa structure is placed in the recessed portion so that the conductive material layer and the second electrode are in at least partial contact with each other, and light emitted from the light-emitting portion is emitted from the second surface side of the first compound semiconductor layer.