A document feeding device including a compact document feeder unit designed primarily for dealing with document sheets of small or standard size and a platen cover unit is disposed on a platen of a copying machine or the like. A small-size document sheet is fed in the forward direction when being supplied onto and discharged from the platen. In a case of handling a large-size document sheet, the sheet is moved backward after being completely introduced into between the feeder unit and platen so as to enter into between the platen cover unit and the platen, and then discharged by being moved forward after copying. Thus, the large-size document sheet can be dealt with similarly to the small-size document sheet by the document feeder unit made compact.