In a spread illuminating apparatus including: an LED at a side surface of a light conductor plate; and an FPC having a land formed on a side thereof for mounting the LED, throughholes are formed at the land, and solder is contained at least partly in each of the throughholes, whereby the LED can be mounted solidly on the FPC with a high precision in height position from the FPC, and at the same time the heat emitted from the LED can be efficiently conducted to a conductive pattern at the rear side of the FPC through an electrode terminal of the LED and the throughholes filled with the solder composed of a metallic material having a high heat conductance.