Abstract: A solid-state image pickup device including a circuit board with an opening, a solid-state image pickup element including a light-receiving surface, a sensor package which accommodates the light-receiving surface and the solid-state image pickup element, and an optical unit including a lens. The solid-state image pickup element, the sensor package, and the optical unit are mounted to the circuit board. In the solid-state image pickup device, the sensor package and the optical unit are disposed so that there is provided an optical path that allows light incident upon the lens to pass the opening and to reach the light-receiving surface at a surface side. By mounting the component parts onto both surfaces, the area of the circuit board can be effectively used, and the size of the solid-state image pickup device in the horizontal direction of the circuit board can be reduced. The optical unit is mounted to the circuit board.