1. An image scanning apparatus comprising: a scanning light source to provide a light to irradiate an object; an image capturing unit disposed opposite to the object; a first driving unit to drive the image capturing unit and the object to move with respect to each other among multiple scanning positions, so as to scan the object; a second driving unit connected to the image capturing unit to drive the image capturing unit to move along a height direction, wherein the height direction is perpendicular to a surface of the object; and an image processing unit electrically connected to the image capturing unit, the first driving unit and the second driving unit, wherein the image capturing unit captures multiple images of the object corresponding to different heights when moving along the height direction at each the scanning position and delivers the multiple images to the image processing unit, and the image processing unit outputs one of the multiple images as one partial image at the scanning position and combines the partial image at each different scanning position to produce a scanned image of the object.