Image forming apparatus having improved mountability of a cartridge while conserving space

An image forming apparatus comprising:

• a cartridge including a photosensitive drum and a grounding member for connecting the photosensitive drum to ground potential;
• an apparatus main body;
• and
• a tray unit to which the cartridge is detachably mounted, and that is configured to be capable of moving with respect to the apparatus main body, between an internal position situated within the apparatus main body and an external position situated outside of the apparatus main body, the tray unit including:
• a first side plate configured to support the cartridge, wherein the first side plate is made of metal, and includes a first inner portion and a first outer side portion, the first inner portion includes a first positioning portion, and the first positioning portion is configured to come into contact with the cartridge to position the cartridge as to an image forming position at which an image forming operation is performed,
• a second side plate configured to support the cartridge, wherein the second side plate is made of metal, and includes a second inner portion and a second outer side portion, the second inner portion is provided with an exposing opening and includes a second positioning portion, and the second positioning portion is configured to come into contact with the cartridge to position the cartridge as to the image forming position, and
• a mounting portion to which the cartridge is mounted, wherein the mounting portion is formed between the first side plate and the second side plate, and, the first inner portion and the second inner portion are situated between the first outer side portion and the second outer side portion in a rotation axis direction of the photosensitive drum of the cartridge mounted to the mounting portion,
• wherein the grounding member is exposed from the mounting portion through the exposing opening so that the grounding member is electrically connected to the apparatus main body in a state where the tray unit is situated at the internal position.