PURPOSE: To recognize a position of an object by turning on alternately each illuminating device and obtaining image data of a shadow of the object to be recognized from a difference of each image data, detecting a corner of a shadow part by executing a scan by a corner detection use pattern and deriving a position of the object to be recognized from the corner.

CONSTITUTION: Each illuminating device 4, 5 placed so as to be opposed to each other in each diagonal upper part seen from an object to be recognized 2 is turned on alternately by a turn-on control means 6, and also, when these illuminating devices 4, 5 are turned on, respectively, an image signal from an image pickup device 3 is received and each image data is stored in image memories 8, 9. Subsequently, a difference of each image data stored in these image memories 8, 9 is derived by a difference image arithmetic means 11, 12 and image data of a shadow of the object to be recognized 2 is obtained, and with respect to the image data of this difference shadow, a corner detecting means 13 detects a corner of a shadow part by allowing a corner detection use pattern to scan. Next, from the corner detected by the corner detecting means 13, a recognizing means 13 recognizes a position of the object to be recognized 2. In such a way, the position of the object can be recognized without being influenced by a wiring pattern and a color, etc.