The invention provides an avalanche photodiode array detector which comprises a first conductive type substrate layer, a PN junction, an isolation structure, at least one anode leading-out end and a cathode leading-out end, a first conductive type semiconductor layer is located on the first conductive type substrate layer, the PN junction is located in the first conductive type semiconductor layer, and the isolation structure is located in the first conductive type semiconductor layer. The projections of the PN junctions on the horizontal plane are provided with interval regions; the isolation structure is located in the first conductive type semiconductor layer and located in the PN junction interval region, and the isolation structure is not in contact with the PN junction. In the invention, the projection of the PN junction of the single pixel on the horizontal plane has the interval region, so that the sum of the widths of the PN junctions of the single pixel is reduced, the whole PN junction region and the region between the PN junctions can absorb incident photons, and the reduction of the heavily doped second conductive type doping layer can improve the absorption of part of short-wavelength photons, so that the photoelectric conversion efficiency is improved. Therefore, the photon detection efficiency of the avalanche photodiode is not affected, and the dark current or dark counting rate of a single pixel is reduced.