An automatic document feeder, which is included in an image reading device and an image forming apparatus, includes first and second document trays, a document output tray, a document conveying passage, multiple document conveying bodies, a drive source, a detector, and a controller. The multiple document conveying bodies include a document holding and conveying body to convey and hold the original document sheet on the second document tray. On detection of the original document sheet on the second document tray while conveying a different original document sheet from the first document tray, the controller stops feeding the different original document sheet, causes the different original document sheet downstream from the document holding and conveying body in a document conveying direction to be conveyed to the document output tray, and stops the drive source after the different original document has been conveyed to the document output tray.