1. A shape measuring apparatus comprising: a characteristic pattern extracting portion, in accordance with a pair of first images of a subject for measurement having characteristic patterns serving as references provided thereon in different angles and a pair of second images of the subject for measurement having no characteristic patterns serving as references provided thereon in the same angles as with the fist images, for calculating the difference between the first image and the second image taken in each direction thereby obtaining the characteristic patterns; positional relationship calculating portion for obtaining a positional relationship between the pair of the first images or the pair of the second images on the basis of the difference images obtained in said characteristic pattern extracting portion; a stereo model forming portion, in accordance with the positional relationship obtained in said positional relationship calculating portion, for mutually relating the fist images or the second images so that a stereo model capable of being stereoscopically viewed is formed; and a shape measuring portion for obtaining the shape of the subject in accordance with the stereo model formed in said stereo model forming portion.