An image scanning device includes a main unit, a scanning unit movable relative to the main unit between its base position and its moved position, a document conveying unit movable relative to the scanning unit between its base position and its moved position, a cover member movable relative to the document conveying unit between its base position and its moved position, and first and second detectors. The first second detectors output four different combinations of on/off signals which include a first combination output in a base state where all the units are in their base positions, a second combination output when the scanning unit moves to its moved position from the base state, a third combination output when the document conveying unit moves to its moved position from the base state, and a fourth combination output when the cover member moves to its moved position from the base state.