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