Patent ID: 8190057

Claim:
An image forming apparatus comprising: a main assembly; a cartridge, which is detachably mountable to said main assembly and includes a photosensitive member on which a toner image is to be formed, that operates so as to form the toner image on a sheet material in a state in which said cartridge is mounted in said main assembly; a fixing unit, completely detachably mountable to said main assembly, that fixes the toner image on the sheet material; and an opening that exposes an inside of said main assembly, wherein said fixing unit and said cartridge are mountable into and demountable from said main assembly in a mounting and demounting direction in which said fixing unit and said cartridge are disposed side by side, wherein, when said fixing unit and said cartridge are mounted into and demounted from said main assembly, said fixing unit passes through said opening, and said cartridge passes through a space in which said fixing unit is to be mounted and passes through said opening, and wherein, when said fixing unit and said cartridge at the time of passing through said opening are projected onto a surface perpendicular to the mounting and demounting direction, a contour of a projected area of said cartridge is at least partly inside a contour of a projected area of said fixing device, and said cartridge passes through the inside of the contour of the projected area of said fixing device when passes through said opening.