In a calibration method for a surface texture measuring instrument which measures a surface of a workpiece and includes an arm that is supported to be swingable around a base point thereof and is provided with a contact point at an end for scanning the workpiece surface, the calibration method includes a measurement step for measuring a calibration gauge of which cross section contains a part of a substantially perfect circle, an assignment step for assigning the detection results, which are obtained in the measurement step, in an evaluation formula based on a circle equation in which the center coordinates of the calibration gauge are (x.sub.c, z.sub.c) and the radius is "r", and a calibration step for calibrating each parameter based on the evaluation formula obtained in the assignment step.