Automatic document feeder and image reading apparatus using the same

An automatic document feeder has a separation roller that separates a document into individual sheets. The document is supplied from a document supply tray. A friction pad is formed to contact one side of the separation roller to supply a friction force for separating the document. A pad holder supports the friction pad. A cover member covers the separation roller. An interlocking unit pressurizes or separates the pad holder toward or from the separation roller in association with an opening or a closing of the cover member. The interlocking unit includes a pinion gear rotating in association with the opening or the closing of the cover member. A rack gear linearly moves in a normal direction of a plane contacting the separation roller and the friction pad according to a rotation direction of the pinion gear. A connecting unit connects the rack gear and the pad holder. An elastic member elastically supports the pad holder to face the separation roller.