To achieve much more accurate and highly reliable road sign recognition by reducing the influence of a deposit even when there exists any deposit on the lens of a photographing device to be used for recognizing a road sign.

A plurality of areas are arranged in a photographic image, and a plurality of bird's-eye images are generated from those areas. When there exists any deposit on a lens, the influence of the deposit always appears at the same position on a bird's-eye image without depending on the state of a road surface. The use of this feature makes it possible to identify the area affected by the deposit on the lens. Therefore, it is possible to remove the bird's-eye image generated from the area affected by the deposit to prevent it from being used for the recognition of the road sign. Thus, it is possible to prevent the deterioration of recognizing performance or erroneous recognition, and to achieve much more highly reliable road sign recognition.