METHOD AND APPARATUS FOR MEASURING ROUGHNESS

PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring a roughness; whereby the surface roughness of a work without a cut-off value indicated can be correctly measured. SOLUTION: An auxiliary storage 34, in which a plurality of cut-off values specified by standards (0.08, 0.25, 0.8 and 2.5 (mm)) are stored, is incorporated in a data processor 14 of the roughness-measuring apparatus 10. These cut-off values are read out by a CPU 28. The CPU 28 calculates a plurality of temporary evaluation values for each of evaluation lengths, corresponding to the plurality of cut-off values from measured data, with the use of a filter having a plurality of cut-off values, and obtains a maximum value from the temporary evaluation values. The CPU 28 controls an evaluation value output means 36 for outputting to a monitor 18, a maximum value of the cut-off value, where the calculated maximum value is present in its roughness range as an effective evaluation value of the roughness of a measuring region.