When a cover portion covers a document table, a document transporting unit is positioned relative to a reinforcing member in the horizontal direction so that the document transporting unit is movable in the vertical direction, and a first vertical positioning member comes into contact with the document table of a reading unit or the periphery thereof to position the document transporting unit in the vertical direction based on the position of the document table. A document height regulating member is positioned relative to the reinforcing member in the horizontal direction so as to be movable in the vertical direction, and a second vertical positioning member comes into contact with the document table to position a regulating member in the vertical direction based on the position of the document table.