A are provided a light source module. The light source module including a light emitting device configured to emit light in a light emitting direction; and an optical device including a first surface disposed over the light emitting device and having a groove recessed in the light emitting direction in a central portion through which an optical axis of the optical device passes, and a second surface disposed opposite to the first surface and configured to refract light incident through the groove to be emitted to the outside. The optical device includes a plurality of ridges disposed on the second surface and periodically arranged in a direction from the optical axis to an edge of the optical device connected to the first surface.