PURPOSE: To reduce the volume of data processing and to shorten a processing time by forming a direction detecting means for detecting the direction of an image to be detected from an angular difference between an extracted angle and a feature angle obtained from a feature angle storing means.

CONSTITUTION: An angle extracted by an angle extracting means 2 is supplied to a means 3 for calculating a straight line passing a virtual reference point so as to be used for the formation of a straight line group passing a virtual reference point together with a feature angle obtained from the feature angle storing means 1. The positional coordinates on a point of each straight line passing a virtual reference point are used by a reference point position coordinate detecting means 4 to detect the reference point position coordinates. The direction detecting means 5 finds out an angle formed by each straight line passing a reference point and a reference line previously set up on an image and detects the direction of the image to be detected from the angular difference between the found angle and the feature angle obtained from the means 1 finding out the straight line passing the virtual reference point used for the fixing said angle. In said processing, the volume of data processing required for the detection of the image to be detected can be reduced.