The present invention provides a photodetector which solves the problem of low sensitivity of a photodetector, an optical communication device equipped with the same, and a method for making the photodetector, and a method for making the optical communication device. The photodetector includes a substrate, a lower cladding layer arranged on the substrate, an optical waveguide arranged on the lower cladding layer, an intermediate layer arranged on the optical waveguide, a optical absorption layer arranged on the intermediate layer, a pair of electrodes arranged on the optical absorption layer, and wherein the optical absorption layer includes a IV-group or III-V-group single-crystal semiconductor, and the optical absorption layer absorbs an optical signal propagating through the optical waveguide.