A light source device including a substrate, a plurality of first light emitting diode (LED) chips, and at least one second LED chip is provided. The substrate has an upper surface. The plurality of first LED chips are disposed on the upper surface and electrically connected to the substrate. Each of the first LED chips includes a first chip substrate, a first semiconductor layer, and a plurality of first electrodes, and the first electrodes are disposed on the upper surface of the substrate. The second LED chip is disposed on the upper surface and electrically connected to the substrate. The second LED chip includes a second chip substrate, a second semiconductor layer, and a plurality of second electrodes. A thickness of the second chip substrate is different from than a thickness of the first chip substrate, and the second electrodes are disposed on the upper surface of the substrate.