To provide both a photodetecting element and a photodetecting device which can prevent generating of a plurality of current paths, and can detect with stability and high sensitivity regardless of a surface state instability of an optical absorption layer. The photodetecting element includes an optically transparent substrate, an optical absorption layer, an electrode, an electrode, an adhesive layer, an insulating film, and a package. The optical absorption layer is formed on the optically transparent substrate, and a part of each the electrodes is embedded in the optical absorption layer. The photodetecting unit is bonded junction down with the adhesive layer on the package. The optical absorption layer absorbs light of a specified wavelength selectively to be converted into an electric signal. The light to be measured is irradiated from a back side surface of the optically transparent substrate.