A scanning apparatus, which supports flatbed and sheet-feeding scanning of document, includes a first scanning unit and a second scanning unit. The first scanning unit includes a first scanning chassis which scans a document in a first main scanning direction. The second scanning unit is disposed beneath the first scanning unit and electrically connected with the first scanning unit. The second scanning unit includes a second scanning chassis which scans a document in a second main scanning direction different from the first main scanning direction. Preferably, the first and the second scanning units provide the flatbed scanning and sheet-feeding scanning functions, respectfully.