To reduce the cost when an optical module which adds or drops a light wave of different wavelength is prepared.

The optical module 1 is equipped with a waveguide unit 2 which holds a waveguide part 5 equipped with an optical waveguide and a filter unit 4 holding the filter 7, the both being fabricated as different components. A filter unit 3 is prepared which has a filter 7 transmitting a light wave to be added or dropped according to the wavelength of the light wave.