An image scanning device includes a first scanner scanning a top side of a transported document at a first scanning position to obtain a first scanned image, a second scanner scanning the back side of the transported document at a second scanning position to obtain a second scanned image, a document feeder transporting a document at the second scanning position at a speed differing from the transportation speed at the first scanning position, and a controller controlling the image scanning device. The controller sets, as a scanning form of a document, either one-side scanning of scanning one side of a document through one transportation, or dual-side scanning of scanning both sides of a document through one transportation. The controller also obtains a set magnification. The controller determines the transportation speed by the document feeder such that, when one-side scanning is set, the scanning magnification in a first direction corresponding to the document transportation direction at the first scanned image attains the set magnification, and when dual-side scanning is set, the scanning magnification in the first direction at the second scanned image attains the set magnification.