A
light source module including a light emitting unit for emitting a
light beam, a light guiding plate, and a light
coupling unit is provided. The light guiding plate has a
first light emitting surface, a first bottom surface, and a
first light incident surface, wherein the
first light emitting surface is opposite to the first bottom surface, and the first light incident surface connects the first light emitting surface and the first bottom surface. The light
coupling unit has a second light incident surface and a second light emitting surface in contact with the first light incident surface. The light emitting unit is disposed beside the second light incident surface. The
light beam enters the light
coupling unit through the second light incident surface, exits the light coupling unit through the second light emitting surface, and then enters the light guiding plate through the first light incident surface.