1. An image processing device for calculating the motion direction of each pixel in a predetermined screen of interest from among a plurality of time series screens, the image processing device comprising: score calculating means for calculating a score corresponding to each of a plurality of motion directions of each pixel in the predetermined screen of interest, based on pixels present in the motion direction across the plurality of the time series screens; and motion direction calculating means for calculating the motion direction of each pixel in the predetermined screen of interest, by processing the plurality of the motion directions based on the scores corresponding to the plurality of the motion directions.