An image processing apparatus for processing an image composed of an effective area as a meaningful area and an ineffective area as a remaining area, includes a left coordinate position detecting unit for detecting a coordinate position of a left-end pixel of pixels that are determined to be out of the ineffective area from among pixels arranged in a vertical line in the image by comparing a pixel value of each pixel with a first threshold value, a right coordinate position detecting unit for detecting a coordinate position of a right-end pixel of the pixels, an upper coordinate position detecting unit for detecting a coordinate position of an upper-end pixel of the pixels, and a lower coordinate position detecting unit for detecting a coordinate position of a lower-end pixel of the pixels.