Image forming apparatus

An image forming apparatus comprising:

• a main body comprising a printing unit for printing an image on a recording medium and a pickup roller for picking up the recording medium;
• a paper feeding device, which comprises an elevatable knock-up plate on which recording media are stackable and a pressure member for elastically pressing the knock-up plate towards the pickup roller, and is removably inserted into the main body;
• and
• a variable guide unit, which is supported by the main body, is fixed in a slope state so as to lower the knock-up plate in a direction away from the pickup roller when the paper feeding device is being withdrawn from the main body, and moves to maintain a contact state with the knock-up plate when the paper feeding device is inserted into the main body,
• wherein the variable guide unit further comprises:
• a variable guide member, which has a slope unit downwardly sloped in a withdrawal direction to lower the knock-up plate in a direction away from the pickup roller by contacting a contact unit of the knock-up plate when the paper feeding device is withdrawn form the main body and is supported by the main body for the slope unit to maintain a contact state with the contact unit due to a rising state of the knock-up plate;
• and
• a fixing member, which is supported by the main body, the fixing member moving to a fixing position for fixing the variable guide member by coupling with the variable guide member when the paper feeding device is withdrawn from the main body and moving to a release position for releasing the variable guide member by decoupling from the variable guide member when the paper feeding device is inserted into the main body.