A paper ejection tray assembly for ejecting paper in an ejecting direction in an image reading device includes a tray body including a stacking surface for stacking an ejected paper, and a pair of movable ribs which are arranged a predetermined distance apart from each other in a direction perpendicular to the ejection direction of the paper and which project out from the stacking surface of the tray body at least when paper is ejected from an ejection slot, the pair of ribs respectively have first inclined surfaces with heights from the stacking surface gradually becoming higher from the downstream side toward the upstream side of the ejection direction of the paper so as to guide the paper ejected from the ejection slot.