PURPOSE: To exactly discriminate the shapes of fruit vegetables by determining the central positions in the transverse direction of the images of the fruit vegetables at plural points and linearly approximating the respective determined central positions in such a manner that the spacing errors between the approximate straight lines to be determined and the respective central positions do not exceed set values.

CONSTITUTION: The images of the fruit vegetables K placed in a horizontally laid posture on a receiving base 7 are picked up by a video camera 23 and the images corresponding to the fruit vegetables K are extracted by an image extracting means 100 in accordance with the picked up image information. The central positions in the transverse direction of the extracted images of the fruit vegetables K are determined by a central position extracting means 101 at the plural points in the longitudinal direction of the fruit vegetables K. The respective determined central positions are linearly approximated by the plural approximate straight lines with a straight line approximating means 102 in such a manner that the spacing errors between the approximate straight lines to be determined and the respective central positions do not exceed the set values. As a result, the ways of bending of the fruit vegetables K are discriminated in the least possible error state.