To achieve a bonding method whereby an angle formed between a surface of an optical element and an upper end surface of a housing side wall can accurately match a design target value. The present invention includes: a step for placing an optical element (12) on a jig (2) such that a surface (12a) is in surface contact with a first flat surface (23a) of the jig (2); and a step for placing a housing (11) on the jig (2) such that an upper end surface (11a1) of a side wall (11a) is in surface contact with a second flat surface (21a) of the jig (2), and a bottom plate (11b) is in contact with a rear surface (12b) of the optical element (12) by having an adhesive (15) therebetween.