An image scanning device of the present invention includes a platen, an image scanning part that scans an image on the manuscript, a light source that irradiates light from the back side of the platen, a platen cover that is allowed to be positioned in a closed state or in an opened state, a light receiving part that is configured to receive light from the manuscript scanning area on the back side of the platen, a range obtaining part that is configured to obtain range between the amount of received light of the light receiving part in the opened state of the platen cover and the amount of received light of the light receiving part in the closed state of the platen cover, and a manuscript detecting part that is configured to detect existence of the manuscript in a manuscript scanning area of the platen based on the range.