Dot pattern perforations predetermined according to a type (kind and carving size) of a workpiece are formed in a part of a body of an attachment where the workpiece is to be set. A seal carving apparatus detects the dot pattern of the mounted attachment by means of photosensors to identify the type of the workpiece. This makes it possible to check consistency between type information on the workpiece input by a customer and type information identified from the dot pattern to prevent mismounting of the attachment or an erroneous carving operation.