PURPOSE: To inspect abrasion by digitizing and programming the shape of a roll and then by finding through measurement the roll shape agreeing with a criterion value by making a comparison to the measured value of the roll shape.

CONSTITUTION: Inspection unit 1 has detection part 5 movable along guide roll 4, and detection part 5, having control arithmetic part 6 incorporated and projection part 7 and photodetection part 8 provided, has its traveling position detected by the position detector in the figure. On the other hand, rolling roll 11 to be inspected is mounted in parallel to the traveling direction of detection part 5 and its caliber 14 is arranged to between projector 7 and photodetector 8 to cut-off the ray zone 15 of light is cut off. Every time the position detector detects the traveling position of detection part 5, control airthmetic part 6 calculates the standard outer roll diameter at the traveling position from a standard pattern, and on the basis of a difference between this outer diameter and a diameter measured at the traveling position, the abrasion of the roll is measured.