Abstract: A scanning device is provided which includes a casing for a chassis to be slidably installed therein. The chassis is mounted with a circuit board having a photoelectric transforming element for performing image scanning and a plurality of switching elements for activating the photoelectric transforming element. The switching elements are capable of being cooperative with a plurality of push-keys installed on the casing, at the time the chassis is positioned at a position where the switching elements are in contact with the push-keys, allowing the switching elements to be pressed by the push-keys when the push-keys are pressed by an external force.