An image forming apparatus includes an image processing part performing a correction process and an image forming part respectively forming first and second images on medium. At a boundary of the first and second images, these images have first and second edge portions. When a first image width of the first image data is narrower than a predetermined width, the first image width is defined as a length determined from one portion of the first edge portion, the image processing part performs the correction process by selectively moving one of the first and second edge portions based on a pixel value of the first image. The image processing part obtains a degree of blackness of the first image based on the pixel value. When the degree of blackness is higher than a predetermined value, the image processing part performs the correction process by moving the second edge portion.