The spot diameter of a laser beam emitted from a first light source, passing through a first stop member, and focused on an object to be scanned is smaller than the spot diameter of a laser beam emitted from a second light source, passing through a second stop member, and focused on an object to be scanned. After the focal depth at the spot diameter of the laser beam emitted from the first light source, passing through the first stop member, and focused on the object to be scanned is adjusted by moving a first holding member holding the first light source at least in the emission direction of the laser beam from the light source, the first holding member and a housing member are bonded with an adhesive, and the first holding member is positioned and fixed to the housing member.