A document feeding device for feeding documents, comprising: a document input tray configured such that documents to be fed are placed thereon; a document output tray configured to receive the documents having been ejected; a feeding mechanism (41, 42,... 49, 50, 51) which is provided for a feeding path connecting the document input tray and the document output tray via a scanning position and feeds each document from the document input tray to the scanning position and from the scanning position to the document output tray; a turnover mechanism (45, 49, 61, 50, 52) which is provided for a turnover path connected to the feeding path and returns the document after passing through the scanning position to a position on the upstream side of the scanning position while interchanging the front end and the rear end of the document in a feeding direction; and an ejection mechanism (50, 51) including a pair of ejection rollers (50, 51) which ejects the document to the document output tray and a switching drive mechanism which relatively moves the projecting part and a nipping position of the pair of ejection rollers (50, 51) in a vertical direction, wherein the ejection mechanism (50, 51) is configured so that its document ejection mode can be switched between a first ejection mode for successively ejecting each document while stacking each document on documents already ejected to the document output tray and a second ejection mode for successively ejecting each document while sliding each document under the documents already ejected to the document output tray, characterized in that the document output tray includes a tray part and a flap part which is attached to the tray part to be pivotable, situated on the upstream side of the tray part in the feeding direction, and is equipped with a projecting part which lifts an upstream end of the already ejected documents regarding the feeding direction from the document output tray in the second ejection mode and a switching drive mechanism pivots the flap part in the vertical direction and wherein the flap part includes a first flap which is attached to the tray part to be pivotable on the upstream side of the tray part in the feeding direction and a second flap which is attached to the first flap to be pivotable on the upstream side of the first flap in the feeding direction and which is equipped with a bent part, and when the flap part pivots upward in the second ejection mode, the bent part of the second flap forms the projecting part, and when the flap part pivots downward in the first ejection mode, the bent part relatively sinks with respect to the second flap compared to its relative position in the second ejection mode due to pivoting of the second flap with respect to the first flap. a document input tray configured such that documents to be fed are placed thereon; a document output tray configured to receive the documents having been ejected; a feeding mechanism (41, 42,... 49, 50, 51) which is provided for a feeding path connecting the document input tray and the document output tray via a scanning position and feeds each document from the document input tray to the scanning position and from the scanning position to the document output tray; a turnover mechanism (45, 49, 61, 50, 52) which is provided for a turnover path connected to the feeding path and returns the document after passing through the scanning position to a position on the upstream side of the scanning position while interchanging the front end and the rear end of the document in a feeding direction; and an ejection mechanism (50, 51) including a pair of ejection rollers (50, 51) which ejects the document to the document output tray and a switching drive mechanism which relatively moves the projecting part and a nipping position of the pair of ejection rollers (50, 51) in a vertical direction, wherein the ejection mechanism (50, 51) is configured so that its document ejection mode can be switched between a first ejection mode for successively ejecting each document while stacking each document on documents already ejected to the document output tray and a second ejection mode for successively ejecting each document while sliding each document under the documents already ejected to the document output tray,