The present invention provides a back illuminated photodetector having a sufficiently small package as well as being capable of suppressing the scattering of to-be-detected light and method for manufacturing the same. A back illuminated photodiode 1 comprises an N-type semiconductor substrate 10, a P+-type impurity semiconductor region 11, a recessed portion 12, and a window plate 13. In the surface layer on the upper surface S1 side of the N-type semiconductor substrate 10 is formed the P+-type impurity semiconductor region 11. In the rear surface S2 of the N-type semiconductor substrate 10 and in an area opposite the P+-type impurity semiconductor region 11 is formed the recessed portion 12 that functions as an incident part for to-be-detected light. Also, the window plate 13 is bonded to the outer edge portion 14 of the recessed portion 12. The window plate 13 covers the recessed portion 12 and seals the rear surface S2 of the N-type semiconductor substrate 10.