A photoelectric conversion element array having a plurality of photoelectric conversion elements (emitting optics 4, receiving optics 5) arranged in an array, and the photoelectric conversion elements 4, 5 are arranged alternately at different positions so that every second one is aligned on the same line in the direction of array. A mounted structure of photoelectric conversion element array, having the emitting optics array and the receiving optics array in the photoelectric conversion element array of this invention, arranged on an interposer substrate 9 so as to oppose therewith, and these arrays are mounted on the interposer substrate 9 through the external connection terminals 7. An optical information processing apparatus 1 having the photoelectric conversion element array of the present invention, and an optical wave guide 3 opposed to the respective optics of the photoelectric conversion element arrays. These configurations not only allow high-density integration of optical interconnects, but also reduce optical interference or crosstalk due to the photoelectric conversion element, and can thereby provide a photoelectric conversion element array allowing efficient propagation of light, an integrated apparatus thereof, a mounted structure of them, and an optical information processing apparatus.