Image forming apparatus

An image forming apparatus, comprising:

• a plurality of photosensitive drums aligning in an aligning direction;
• a housing including:
• a first wall having a first opening;
• and
• a second wall having a second opening, the second wall facing the first wall in the aligning direction;
• a transfer unit including:
• a first roller located closer than the second wall to the first wall;
• a second roller located closer than the first wall to the second wall;
• an intermediate transfer belt strained around the first roller and the second roller;
• a plurality of primary transfer rollers located between the first roller and the second roller in the aligning direction, each of the plurality of primary transfer rollers nipping the intermediate transfer belt at a position between the primary transfer roller and a corresponding one of the plurality of photosensitive drums;
• and
• a secondary transfer roller located at a lower position with respect to the second roller, the secondary transfer roller nipping the intermediate transfer belt at a position between the secondary transfer roller and the second roller;
• a fuser located between the second roller and the second wall;
• a first sheet tray configured to support a sheet being inserted through the first opening of the first wall;
• a second sheet tray movable between a closure position, in which the second sheet tray closes the second opening of the second wall, and an open position, in which the second opening is open, the second sheet tray being configured to support the sheet passing through the fuser when the second sheet tray is at the closure position.