Image forming apparatus

The invention provides an image forming apparatus which enables a user to easily recognize wrong installation of a belt unit through a simple structure. An image forming apparatus (1) includes: an apparatus main body (100); a fixing unit (40) that is attachable to the device main body (100) in the first direction; and a transfer unit (20) as a belt unit that can be attached to an attachment position within the device main body (100) in a second direction intersecting the first direction. The transfer unit (20) has a protrusion (31a) as a restricting portion that restricts attachment of the fixing unit (40) when the transfer unit (20) is located at a first abnormal position different from the attachment position. 图像形成装置，能够以简单的结构使用户容易地识别出带单元的误安装。图像形成装置(1)具有：装置主体(100)；定影单元(40)，其能够在第1方向上安装于装置主体(100)；以及作为带单元的转印单元(20)，其能够在与第1方向交叉的第2方向上安装于装置主体(100)内的安装位置。转印单元(20)具有作为限制部的突起(31a)，该突起(31a)在转印单元(20)位于与安装位置不同的第1非正常位置的情况下，限制定影单元(40)的安装。