A light source device which is used as the backlight device and does not generate sound is provided. One or more flat substrates each having a light emitting element on its surface side are supported by a chassis having a conductive flat plate surface so that back surfaces of the substrates are opposed to the flat plate surface. The substrate comprises first wiring conductive thin films on a surface side of an insulation substrate, and one or more second radiating or wiring conductive thin films on a back surface side of the insulation substrate. Two terminals of the light emitting element are connected to the two adjacent first conductive thin films. A potential of at least one of the second conductive thin films is fixed to have a constant potential difference or preferably fixed to the same potential with respect to that of the flat plate surface of the chassis.