A type detecting part detects types of drawing objects included in a printing job. A rate detecting part detects a rate of each type of drawing object. A storing part stores the rate of each type of drawing object as a count value of a statistics counter which counts predetermined units of drawing objects for each type of drawing object. A comparing part compares a previously set printing quality with a recommended printing quality which is derived from count values of statistics counters. A changing part changes the previously set printing quality to the recommended printing quality when the previously set printing quality is different from the recommended printing quality.