A light detection device which can be stably surface-mounted on, for example, a circuit board or the like, and a mounting method thereof are provided. A light-receiving element includes, a transparent conductive electrode (first electrode), a semiconductor layer, and an electrode (first electrode), which are sequentially laminated on a transparent substrate. An insulative substrate includes a terminal electrode (second electrode) which is provided to be exposed at first and second faces of the insulative substrate. The light-receiving element is disposed at the first face of the insulative substrate, and the transparent conductive electrode and the electrode are electrically connected with the terminal electrode exposed at the first face of the insulative substrate. Hence, the light detection device with this structure is surface-mounted on the circuit board such that the terminal electrode exposed at the second face of the insulative substrate connects with an external terminal of the circuit board.