A light source module including a light guide plate, a plurality of light emitting devices, and a plurality of first reflective devices is provided. The light guide plate has a plurality of through holes and a light emitting surface. The through holes pass through the light emitting surface. Each of the through holes has a first side wall and a second side wall opposite the first side wall. At least one of the light emitting devices is disposed in each of the through holes. Each of the light emitting devices is capable emitting a light beam. The light beam enters the light guide plate from the first side wall of the through hole which the light emitting device is disposed in and leaves the light guide plate from the light emitting surface. The first reflective devices are disposed on the second side walls of the through holes.