Abstract: A locking device is proposed for scanner having an optical module. The optical module has a base and an image scanning means arranged on one side of the base. A locking hole and a mounting portion for the locking device are provided at predetermined locations on the image scanning means and the base, respectively. The mounting portion is a through hole piercing the base. The locking device is arranged within the mounting portion and the upper portion of the locking device is engaged within the locking hole. By using a locking device wherein the upper end thereof detaches from the locking on the scanner when the lower end thereof is pivotally rotated by the pushing force from table, the scanning means of the scanner can move laterally. The image scanning means is not shifted during portage.