An image processing device for dividing an image imaged by imaging means into multiple regions includes: processing means for grouping, when difference of the pieces of image data between a single pixel within the image and a pixel adjacent thereto is less than a predetermined threshold, the single pixel and the adjacent pixel, and dividing the image into multiple regions with finally obtained each group as each region of the image; and average-value calculating means for calculating the average value of the image data within the group including the single pixel; with the processing means comparing the image data of the single pixel, and the average value calculated at the average-value calculating means regarding the group to which the adjacent pixel belongs; and when the difference thereof is equal to or greater than a predetermined second threshold, doing not group the single pixel and the adjacent pixel.