Provided is an optical module including a light source for generating an optical signal, a waveguide for waveguiding the optical signal, a photodetector for detecting the optical signal, a first reflecting mirror on the light source for reflecting the optical signal generated by the light source to a side of the waveguide, and a second reflecting mirror on the photodetector for reflecting an optical signal emitted from the waveguide in a vertical downward direction. The photodetector detects an optical signal reflected by the second reflecting mirror.