Provided is an automatic document conveying device, including: a document feeding portion that feeds a document from a document stacking tray; a conveying portion that conveys the document which is fed, to a document reading portion; a discharge portion that discharges the document after being read to a discharge tray; a branching guide that switches a conveying path so that a second surface is read after a first surface of the document is read; and a switchback portion including a switchback roller pair for sending the document to the conveying portion again after the conveying path is switched by the branching guide, in which a switch of the conveying path by the branching guide and open/close of a nip of the switchback roller pair are performed in one drive portion.