An optical module includes a light-forming part configured to form light; and a protective member that includes an output window configured to transmit light from the light-forming part and that is disposed so as to surround the light-forming part. The light-forming part includes a base member; a plurality of semiconductor light-emitting devices mounted on the base member and configured to emit light differing from each other in wavelength; and a filter mounted on the base member and configured to directly receive and coaxially multiplex diverging light from the plurality of semiconductor light-emitting devices.