PURPOSE: To improve a detecting efficiency by searching the maximum value of a peak difference searched for each of plural directivities, and using the directivity having the maximum peak difference as the directivity of a position under consideration.

CONSTITUTION: A picture signal 50 is inputted to a direction 1 adding circuit, direction 2 adding circuit, and ... direction (n) adding circuit, and plural picture values are integrated, and a directional integration is calculated along an angle corresponding to a direction (j) by a direction (j) adding circuit. For example, when the kinds of the directivity is 3, the number of picture elements to be added is 4, and the number of the directional integration is 3 or 2, the three directional integration is inputted to a peak difference detecting circuit h1 as a signal 51, two directional integration is inputted to a peak difference detecting circuit h2, and two directional integration is inputted to a peak difference detecting circuit h3. Moreover, the output of each peak difference detecting circuit h1-h3 is inputted to a maximum value judging circuit 10, the maximum value of the peak difference is searched, the directivity whose peak difference is the maximum is used as the directivity of the position under consideration and outputted as a signal 52.