1. An image processing device, to which pixel signals of a plurality of adjacent pixels are simultaneously input, configured to simultaneously find correlations between a plurality of target pixels adjacent to each other and corresponding reference pixels with pixels around the plurality of target pixels for each of the plurality of target pixels, the image processing device comprising: a common region sum of absolute differences (SAD) calculation unit configured to define each of a common target region in which a plurality of target regions predetermined for each of the plurality of target pixels adjacent to each other to be simultaneously correlated overlap and a common reference region corresponding to the common target region and in which a plurality of reference regions predetermined for each of reference pixels corresponding to the plurality of target pixels overlap, and output a common SAD calculation result obtained by performing SAD calculations based on values represented by pixel signals of pixels included in the defined common target region and the defined common reference region; and addition processing units equal in number to the plurality of target pixels adjacent to each other to be simultaneously correlated and configured to correspond to the plurality of target pixels and output SAD calculation results obtained by performing addition processes based on the common SAD calculation result and an SAD calculation result corresponding to a region of a peripheral pixel which is not included in the common target region within a predetermined target region for the plurality of target pixels to which the addition processing units correspond, wherein the common region SAD calculation unit comprises calculation circuits, and the imaging process device is configured to reduce a number of the calculation circuits provided in the common region SAD calculation unit.