PURPOSE: To rapidly and highly accurately cope with various stamped characters and to identify the characters with high accuracy by selecting a circumscribing frame according to a picture pattern formed based on a provisional binarization signal, calculating a second threshold value based on the variable density level of the picture of a reflected light situated on this circumscribing frame and binarizing.

CONSTITUTION: The stamped character is irradiated so as to provide an even illuminance on a character stamped face 32, the circumscribing frame of an initially relevant type is selected according to the picture pattern formed by a provisional binarizing means 51, an optimum binarizing means 52 calculates the second threshold value based on the variable density level of the picture of the reflected light situated on this circumscribing frame and the picture signal in the selected circumscribing frame is binarized. Thereby, the various stamped characters are rapidly and highly accurately coped with, an area divided picture obtained by binarizing is divided to meshes to calculate the area ratio of picture elements, compare with the picture element area of the circumscribing frame of a standard character pattern and select the standard character pattern, so that the character can be properly recognized without receiving an influence such as the thickness of the character.