A light source device and projector using the same is provided. The light source device includes multiple light source modules and a multi-channel optical light tube. The multi-channel optical light tube includes multiple channels, each of which has a light guiding portion and corresponds to one or more of the light source modules. The light source module transmits the output light to the corresponding light channel, and the light guiding portion of each light channel is provided with a reflective surface for combining the light input through the light channels to the multi-channel optical light tube, thus providing the output of the light source device.