1. An image taking device for taking an image of an object by focusing reflected light from the object on a light receiving portion, comprising: a measuring portion that measures distances between the image taking device and at least two points in a subject surface of the object; an exposure control portion that controls exposure time of the light receiving portion upon taking the image in accordance with at least one of the distances measured; a posture determining portion that determines whether the subject surface is perpendicular to an axis along a shooting direction of the image taking device in accordance with the distances measured; and an image taking portion that takes the image if it is determined by the posture determining portion that the subject surface is perpendicular to the axis and one of the distances measured is within a predetermined range.