PURPOSE: To provide a mark cutting-off method which does not make wrong recognition even if a picture pattern or the like is interposed between marks.

CONSTITUTION: This is a method by which a prearranged cutting-off place is indicated by means of a mark 12 printed on a sheet material 10 and a mark 12 is watched by means of two sensors 14, 16 arranged in slip in a material flow direction and in a width direction and a sheet cutting-off command is given to a cutter by means of the detection signals of both sensors, and the value setting of time series data consisting of a mark width value A, an intermark space value B, a space value C to a picture pattern 18, or the like that are known is conducted in a data setter 20, and pattern data evaluated regarding a mark is made to be able to be outputted, and signals from both sensors 14, 16 are synthesized into of signal in a synthetic circuit 24, and time series data regarding a mark is evaluated, and pattern data and time series data that are evaluated, are compared with each other in a pattern comparator 22, and when the value patterns of both coincide with each other, a sheet cutting-off command is given.