PURPOSE: To provide the simple and fast vehicle registration number recognizing method which can perform character recognition by the same algorithm for four different cases of the normal license plates of a commercial vehicle and a private vehicle and self-illuminating license plates in an illumination and a nonillumination state.

CONSTITUTION: A video camera picks up an image of a vehicle travel path and a vehicle is lighted (S2) in response to vehicle detection (S1); and the image including the front scene or rear scene of the traveling vehicle which is being lit is taken in (S3), an edge extracting process is performed (S4) for the taken-in image, and the character area of the license plate is extracted (S5). Then the area inside the character part is reversed (S6) and respective characters are recognized (S7). This method includes said processes in order.