A light source module including a light guide plate, a light source set and a light modulating device is provided. The light guide plate includes a light entering surface. The light source set is disposed beside the light entering surface. The light-source is adapted to emit a first light beam. The light modulating device is disposed between the light source set and the light guide plate. The light modulating device includes a light reflection portion. The first light enters the light entering surface through the light modulating device, and the light modulating device makes the divergence angle of the first light converge.