A light source module includes a first frame, a second frame, a light guide plate, a light source, at least one positioning element and at least one buffer element. The second frame is disposed corresponding to the first frame and has at least one through hole. The light guide plate is disposed between the first frame and the second frame and has a light incident surface and a side surface, and the side surface faces to the through hole of the second frame. The light source is disposed on the light incident surface of the light guide plate. The positioning element is disposed in the through hole of the second frame. The buffer element is located between the positioning element and the side surface of the light guide plate.