Disclosed is a fixing module for fixing an optical system to an optical apparatus, including a coupling unit having a plate to couple to the apparatus, the coupling unit having a first penetrating space at a central portion thereof and a protruding portion protruded downwards from the plate; a first fixing unit combinable with the coupling unit and having a receiving space including a thermosetting resin such that the protruding portion is fixed into the thermosetting resin; and a second fixing unit combinable with the first fixing unit and having a second penetrating space communicating with the first penetrating space, such that the optical system can penetrate through the first and the second penetrating spaces and be fixed by the second fixing unit.