Dots (14) are marked on the stage surface of a stage (13) beforehand, and when an original (5) is placed on that stage, a document camera (1) acquires stage specification information such as the number of pixels of an image of the dot (14) and that of a check area (82) of the image thereof, based on the resolution of a shot image obtained by shooting. Based on the acquired stage specification information, the document camera (1) identifies an area of an image of the stage (13), acquires a binarized image which represents the area of the image of the stage (13) in white, so that a boundary between an area of an image of the original (5) and the area of the image of the stage (13) becomes clarified. Based on the binarized image, the document camera (1) determines the outline of the image of the original (5), and acquires the image thereof.