In an image forming apparatus which requires the user to manually input sheet medium information, (when a bundle of sheets which include a plurality of types of print media are to be printed, the user must manually input setups of the image forming apparatus for each individual print medium. In manual setups by the user, some setups require user's knowledge about print media. When the user has made wrong setups, a print result cannot be obtained under an appropriate control condition Furthermore, when information about a print medium is sensed by the sensor without manual setups, the information cannot be often precisely detect depending on the type and thickness of the print medium, an environment, and the like, and it is consequently difficult to attain optimal image formation. It is an object of this invention to attain optimal image formation, saving user labor and shortening the print time by using a radio tag attached to the sheet medium. An image forming apparatus which forms an image on a sheet medium, has means for reading information from a information holding means, such as a minuscule radio chip, attached to the sheet medium, and means for manually inputting information of the sheet medium, and controls an image forming condition using either information.