To provide a method and apparatus capable of measuring a protrusion length of a protrusion portion on each side of a sheet after cutting even when there is variation in positions of cords embedded in the sheet, the apparatus is provided with imaging means that images a cross-sectional profile in a width direction of the sheet including the protrusion portions, and is arranged to generate waveform data from the imaging of the cross-sectional profile, detect maximum height positions of crests and minimum height positions of troughs of the waveform data, set, based on the waveform data, a maximum height position of a crest closest to a width end of the sheet as a maximum height position of an end crest, set a position corresponding to an edge of the protrusion portion of the sheet, which is located on more width end side than the maximum height position of the end crest, as a minimum height position of a terminal trough, detect a distance in the width direction of the sheet between the maximum height position of the end crest and the minimum height position of the terminal trough, and measure the protrusion length of the protrusion portion based on the detected distance.
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