A light illuminating apparatus comprising multiple light emitting devices wherein each of the light emitting device comprises: a substrate (410, 1710) having an anode pattern and a cathode pattern; and at least one light emitting element (330, 330A, 1600, 1600A) connected to the anode pattern and the cathode pattern, wherein the substrate (410, 1710) has a connecting part at each of two ends of the anode pattern extending in a connection direction with other light emitting device that is different from the light emitting device to connect the light emitting device to other light emitting device, and a connecting part at each of two ends of the cathode pattern extending in the connection direction to connect the light emitting device to other light emitting device, wherein the multiple light emitting devices include a first light emitting device and a second light emitting device adjacent to the first light emitting device, and the connecting part installed on the cathode pattern of the first light emitting device and the connecting part installed on the anode pattern of the second light emitting device are to be electrically connected, or the connecting part installed on the anode pattern of the first light emitting device and the connecting part installed on the anode pattern of the second light emitting device are to be electrically connected, and the connecting part installed on the cathode pattern of the first light emitting device and the connecting part installed on the cathode pattern of the second light emitting device are to be electrically connected, the connection condition of the light emitting devices is shiftable between series connection and parallel connection, characterized in that each of the connecting part includes a screw hole. a substrate (410, 1710) having an anode pattern and a cathode pattern; and at least one light emitting element (330, 330A, 1600, 1600A) connected to the anode pattern and the cathode pattern, wherein the substrate (410, 1710) has a connecting part at each of two ends of the anode pattern extending in a connection direction with other light emitting device that is different from the light emitting device to connect the light emitting device to other light emitting device, and a connecting part at each of two ends of the cathode pattern extending in the connection direction to connect the light emitting device to other light emitting device, wherein the multiple light emitting devices include a first light emitting device and a second light emitting device adjacent to the first light emitting device, and the connecting part installed on the cathode pattern of the first light emitting device and the connecting part installed on the anode pattern of the second light emitting device are to be electrically connected, or the connecting part installed on the anode pattern of the first light emitting device and the connecting part installed on the anode pattern of the second light emitting device are to be electrically connected, and the connecting part installed on the cathode pattern of the first light emitting device and the connecting part installed on the cathode pattern of the second light emitting device are to be electrically connected, the connection condition of the light emitting devices is shiftable between series connection and parallel connection, characterized in that each of the connecting part includes a screw hole.