A light emission detection device having a flow path from which light to be detected is emitted is provided. The device includes a detection-side substrate having a joining surface and a detection surface provided opposite the joining surface, the joining surface having a depression and a light-shielding film provided over an area excluding the depression, the depression forming the flow path, the detection surface transmitting the light emitted from the flow path; and a wiring-side substrate having a joining surface and a conductive pattern provided with a varying thickness on the joining surface, the joining surface of the wiring-side substrate joining the joining surface of the detection-side substrate. In the area over which the light-shielding film is provided, adhesive is provided with a thickness corresponding to the varying thickness of the conductive pattern and the detection-side substrate and the wiring-side substrate are closely joined to each other with the adhesive.