Image processing device for recognizing outline of moving target and method therefor

An image processing device is provided, which has the capability of accurately recognizing the outline of a moving target from at least four still images taken in times series without using a background image not including the moving target. This device comprises a first operation unit for outputting a processed outline image by use of a reference image taken at a reference time, a pair of images taken at first and second times other than the reference time, a second operation unit for outputting a processed outline image by use of the reference image and an image taken at a third time different from the reference time, the first time and the second time, and an outline extracting unit for extracting the outline of the moving target from these processed outline images.