The image forming device includes an image formation request accepting section, an image data acquisition section, a readability improvement request accepting section, an area discriminating section, a line width measuring section, a correction object extracting section, a correction processing section, and an image forming section. The area discriminating section discriminates between a line drawing area and an area other than the line drawing area in the image data, and extracts a letter and a line. The line width measuring section measures the line width of the line or the letter. The correction object extracting section extracts an area where the line width measured by the line width measuring section is lower than the predetermined threshold as a correction object. The correction processing section broadens the width of the area determined as the correction object up to the predetermined value, to form corrected data for printing.