An image processing apparatus includes a binarization unit that binarizes a selected image region based on prescribed criteria into an image trimming target white pixel region and a background black pixel region, a hole filling unit that fills a hole of the white pixel region by converting a black pixel surrounded by the white pixel region into the white pixel, a distance conversion unit that calculates a distance value from each white pixel to the black pixel region, a skeleton extraction unit that extracts points indicating a skeleton of the white pixel region according to each distance value, and a trimming outline determination unit that excludes a less significant point based on prescribed conditions, draws an oval or perfect circle according to each distance value, centered at a non-excluded point, and determines an outer edge of ovals or perfect circles as an outline for trimming a trimming target image.