Patent ID: 8478151

Claim:
An image forming apparatus comprising: a first image forming unit configured to form an image on a sheet with a first material that is not erasable by heating; a second image forming unit that is located on a downstream side in a sheet conveying direction from the first image forming unit, the second image forming unit configured to form an image on the sheet with a second material that is erasable by heating to an erasing temperature; a fixing device that is arranged between the first image forming unit and the second image forming unit, the fixing device configured to fix the image with the first material on the sheet by heating the sheet at a fixing temperature lower than the erasing temperature in a fixing process, and configured to heat the sheet above the erasing temperature in an erasing process; a first sheet feeding unit arranged on an upstream side in the sheet conveying direction of the first image forming unit and configured to feed a sheet; a second sheet feeding unit arranged on a downstream side in the sheet conveying direction of the fixing device and on an upstream side in the sheet conveying direction of the second image forming unit, the second sheet feeding unit configured to feed the sheet to a position; a detecting unit configured to detect the sheet in the second sheet feeding unit; and a control unit configured to cause the second image forming unit to form the image with the second material on the sheet fed from the second sheet feeding unit, and to cause, if the detecting unit detects the sheet in the second sheet feeding unit, the second sheet feeding unit to feed the sheet to the second image forming unit, and configured to cause, if the detecting unit does not detect the sheet in the second sheet feeding unit, the first sheet feeding unit to feed the sheet to the second image forming unit.