A sheet feeder comprising: a feed roller which feeds sheet by rotating in contact with the sheet; a separation roller which is disposed at a downstream side of a sheet feeding direction; a supporting member which supports the feed roller and the separation roller, the supporting member is supported so as to be swingable around the rotation axis of the separation roller; a drive source which drives the supporting member so as to swing; an arm pivot which is disposed between the drive source and the supporting member; a first arm which is disposed at a side of the drive source; and a second arm which is disposed at a side of the supporting member, the second arm is able to be separated from the first arm; wherein the first arm and the second arm are integrally swung around the arm pivot by the drive source, thereby the supporting member swinging.