To measure the information on the shape of a specific area in an image with accuracy.

A border extracting device extracts the information on the positions of five or more estimated border points of the specific area which is considered to originally have an elliptic shape in the image based on the feature of the image pattern of the specific area (step 105). Then an ellipse approximating device calculates an ellipse approximated to the original elliptic shape of the specific area by considering that the specific area originally has the elliptic shape based on the extracted information on the positions of the estimated border points (steps 106 and 107). Consequently, the information on the shape of the specific area can be measured with accuracy.