Image forming apparatus

An image forming apparatus comprising:

• a drum unit attachable to and detachable from a main housing, and including a photosensitive drum on which an electrostatic latent image is formed and a drum frame which supports the photosensitive drum;
• a development unit including a development roller which carries a toner and a development housing which supports the development roller;
• a supporting part which supports the development unit so as to be shiftable in directions close to and separate from the drum unit;
• and
• a biasing part provided in the main housing, and biasing the development housing toward the drum unit, wherein
• the drum unit is attachable to and detachable from the main housing in an attachment direction crossing to a shift direction of the development direction and crossing to an axial direction of the development roller,
• when the drum unit is not attached to the main housing, the development unit is biased by the biasing part and is positioned closer to the drum unit than a predetermined position of the development unit when the drum unit is attached, and
• when the drum unit is attached to the main housing, the drum frame pushes away the development housing against a biasing force of the biasing part to shift the development unit to the predetermined position.