Fixing device, single-sided image forming apparatus, and double-sided image forming apparatus

A fixing device comprising:

• a fixing device body that is adapted to attach to and detach from an apparatus body of a double-sided image forming apparatus which comprises a return passage through which a recording medium is returned to an image forming position in order to form an image on both sides of the recording medium, and of a single-sided image forming apparatus which does not comprise the return passage;
• a fixing member that is provided in the fixing device body and that fixes an image to the recording medium;
• and
• a first attachment section that is provided at a return passage side in the fixing device body and that is adapted to have a passage surface member, which comprises a passage surface of an introduction passage through which a fixed recording medium on which an image has been fixed by the fixing member is introduced into the return passage, attached thereto.