In a calibration method for a surface texture measuring instrument which measures the 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 the cross section of which contains a part of a substantially perfect circle, an assignment step for assigning the detection results from the measurement step in an evaluation formula based on the equation of a circle in which the center coordinates of the calibration gauge are (x c , z c ) and the radius is "r", and a calibration step for calibrating each parameter based on the results obtained in the assignment step.