An application amount of developer on a printing medium on which a page that is to be processed has been formed is obtained based on image data that includes a plurality of pages, and based on the image data, a coverage ratio of the developer on a printing medium on which a predetermined page has been formed is obtained. Then, setting temperatures of the heater that respectively correspond to the application amount and the coverage ratio are obtained, and the temperature of the heater is controlled based on the measured actual temperature of the heater and the obtained setting temperatures of the heater, thereby performing control to subject the printing medium on which the page that is to be processed has been formed to fixing.