A document feeder includes a lift plate, a storage section, and an operation display section. The lift plate lifts a document sheaf up to a feed position. The storage section stores a first travel amount. The first travel amount is a travel amount of the lift plate necessary for the lift plate to cause the document sheaf to arrive at the feed position in a situation in which the document sheaf has a maximum permitted thickness. When a second travel amount is less than the first travel amount, the operation display section informs that the number of the document sheets in the document sheaf exceeds a maximum sheet number. The second travel amount is a travel amount of the lift plate taken to cause the topmost part of the document sheaf to arrive at the feed position.