An array structure solves issues that exist in conventional compound semiconductor photodiode arrays, such as large cross talk, large surface leaks, large stray capacitance, narrow detection wavelength bands, and bad manufacturing yield, simultaneously. A photodiode array has, laminated upon a semiconductor substrate, a buffer layer (8) with a broad forbidden band width, an I-type (low concentration photosensitive layer (2) with a narrow forbidden band width, and an n-type semiconductor window layer (3) with a broad forbidden band width, wherein photodiode elements are electrically separated from adjacent elements, by doping the periphery of the p-type impurity, and the detection wavelength band is expanded, by making the n-type window layer (3) on the photosensitive layer (2) a thinner layer with crystal growth.