A light source module includes a light guide plate, a light source, a first prism sheet, a second prism sheet and a third prism sheet. The light guide plate includes a light emitting surface, a bottom surface and a light incident surface. The light source is disposed on the light incident surface and emits a beam into the light guide plate through the light incident surface. The first prism sheet is disposed on the light emitting surface and includes a plurality of first prism units located between the light emitting surface and the second prism sheet. The second prism sheet includes a plurality of second prism units extending in a first direction and located between the first prism sheet and the third prism sheet. The third prism sheet includes a plurality of third prism units extending in a second direction. The first direction is perpendicular to the second direction.