An automatic document conveying device to be applied to an image processor with a transparent plate on which to place document to be processed being disposed on the upper surface of a housing. The automatic document conveying device comprises a document table, a document introduction passage extending from the document table to one end edge of the transparent plate, a first document receiving tray, a second document receiving tray and a document delivery passage. The document delivery passage includes a common passage extending from the other end edge of the transparent plate, a first branched passage extending from the downstream end of the common passage to the first document receiving tray, and a second branched passage extending from the downstream end of the common passage to the second document receiving tray. The automatic document conveying device further includes a docunent sending means for delivering a plurality of documents on the document table piece by piece to the document introduction passage, a document introduction means for introducing the document sent out to the document introduction passage onto the document plate, a document conveying means for conveying the document along the transparent plate, and a document discharging means for discharging the document delivered to the common passage of the document delivery passage by the document conveying means through the common passage, the first branched passage or the second branched passage in the document delivery passage.