An optical filter module of the present invention has a flat substrate, an optical path formed on the flat substrate; a filter insertion groove provided, crossing the optical path, on the flat substrate; a multilayer filter inserted, dividing the optical path, into the filter insertion groove; and a pair of covers disposed on the flat substrate so as to sandwich the multilayer filter. The present invention enables the omission of the process of adjustment of the optical axis, thus achieving high operability. At the same time, the present invention ensures fixing and mounting of the multilayer filter even if the multilayer filter is warped.