A light source device comprising: a base substrate ; a plurality of light emitting elements disposed on the base substrate along each of a first direction (X) and a second direction (Y) crossing the first direction; and a first polarity terminal and a second polarity terminal for supplying power to the plurality of light emitting elements, wherein the first polarity terminal and the second polarity terminal project from one side of the base substrate in the first direction (X) as viewed in a third direction (Z) crossing the first direction and the second direction, wherein the base substrate is formed in a rectangular shape in a plan view, the first direction (X) is a direction crossing one side of the rectangular shape, and the first polarity terminal and the second polarity terminal project from the one side as viewed in the third direction (Z), wherein the plurality of light emitting elements are disposed such that a plurality of light emitting element groups each composed of one row of the light emitting elements disposed along the first direction (X) are disposed along the second direction (Y), and the light emitting elements in the one row in each light emitting element group are connected in series, the light source device further comprising holding portions disposed on the base substrate and each holding a said light emitting element group such that the light emitting elements emit light to the side opposite to the base substrate, wherein the holding portion includes a first surface on which the light emitting element group is disposed, and a second surface different from the first surface, and a wiring layer to which the second polarity terminal is connected is provided on the second surface. a base substrate ; a plurality of light emitting elements disposed on the base substrate along each of a first direction (X) and a second direction (Y) crossing the first direction; and a first polarity terminal and a second polarity terminal for supplying power to the plurality of light emitting elements, wherein the first polarity terminal and the second polarity terminal project from one side of the base substrate in the first direction (X) as viewed in a third direction (Z) crossing the first direction and the second direction, wherein the base substrate is formed in a rectangular shape in a plan view, the first direction (X) is a direction crossing one side of the rectangular shape, and the first polarity terminal and the second polarity terminal project from the one side as viewed in the third direction (Z), wherein the plurality of light emitting elements are disposed such that a plurality of light emitting element groups each composed of one row of the light emitting elements disposed along the first direction (X) are disposed along the second direction (Y), and the light emitting elements in the one row in each light emitting element group are connected in series, the light source device further comprising holding portions disposed on the base substrate and each holding a said light emitting element group such that the light emitting elements emit light to the side opposite to the base substrate, wherein the holding portion includes a first surface on which the light emitting element group is disposed, and a second surface different from the first surface, and a wiring layer to which the second polarity terminal is connected is provided on the second surface. <EOS>