It is important to not only evaluate granularity but also clarify the factors affecting it in order to improve the graininess of an image. A method for separating graininess into elements on the basis of the fluctuation of the background, lightness, and toner adherent area is proposed. By using this method following estimations will be enabled; 1. By obtaining the relation between the ordinary graininess and elements, the effect of each elements to the image quality can be estimated. This makes it possible to categorize printer. 2. Measuring by means of a polarizing plate, an effect of gloss ununiformity to the image quality can be detected. 3. By defining the standard contrast for a monochrome image, even though the dot density differs, the area fluctuation factor of graininess can be compared.