An attachment structure for installing a lighting device on an attachment target, includes a hole formed in a bottom surface of the attachment structure for letting light from the lighting device pass through the hole, and a plurality of ribs formed around the hole. The plurality of ribs are substantially flush with each other in a lighting device placement area configured to receive a bottom surface of the lighting device, so that the lighting device is positioned with respect to the bottom surface of the attachment structure in a height direction of the lighting device.