Provided is an optical module capable of inhibiting both the displacement of an optical axis caused by thermal changes and property degradation in an optical functional circuit. The optical module includes: a planar lightwave circuit including a waveguide-type optical functional circuit and a waveguide region where only an optical waveguide is formed in contact with a side, wherein an emission end face where output light is emitted from the optical functional circuit, or an entrance end face where input light is entered to the optical functional circuit is formed in contact with the side; a fixing mount employed to hold the planar lightwave circuit only in the portion where the waveguide area is located; and an auxiliary mount employed to hold the planar lightwave circuit in contact with a side that is opposite the side where the emission end face or the entrance end face.