A method for calibrating a surface texture measuring instrument that measures a surface of a workpiece, the instrument including: an arm supported to be swingable around a base point; a stylus that is arranged on an end of the arm and is provided with a contact point on a tip thereof, the contact point being in contact or nearly in contact with the workpiece along a substantial tangent line of an arc drawn by a tip of the contact point in accordance with a swing of the arm; a shifter for shifting the arm in x-direction that is along the surface of the workpiece while keeping the contact point in contact or nearly in contact with the workpiece surface; a first detector for detecting a displacement of the base point in the x-direction; a second detector for detecting a displacement in z-direction that is orthogonal to the x-direction due to the swing of the arm based on a displacement of a point on the arm in the z-direction; and a compensation computing unit that compensates detection results (x i) of the first detector and detection results in form of a first displacement (z i) of the second detector for a deviation (dx, dz) due to the swing to obtain measurement data of the surface of the workpiece, the method comprising: 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 (xi) of the first detector and the first displacement (zi) in a form of the detection results of the second detector, which are obtained in the measurement step, in an evaluation formula (f i) based on a circle equation in which the center coordinates of the calibration gauge are (x c, z c) and a radius of the calibration gauge is r; and a calibration step for calibrating a gain (g) for converting the first displacement (z i) of the point on the arm in the z-direction detected by the second detector into a second displacement of the tip of the contact point in the z-direction, and each parameter included in the deviation (dx, dz) based on the results obtained in the assignment step, wherein the evaluation formula (f i) in the assignment step is determined based on: an arm reference length as a length from the base point to a reference point as a foot of a perpendicular line extended from the tip of the contact point to a base line extending in longitudinal direction of a base shaft of the arm; a detection value (x i) of the first detector; the first displacement (z i); the gain (g); and a tip compensation amount (h) as a length from the reference point to the tip of the contact point, and wherein, with the known arm reference length being given, the center coordinates (x c, z c), the radius (r), the gain (g), and the tip compensation amount (h) are found in the calibration step. 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 (xi) of the first detector and the first displacement (zi) in a form of the detection results of the second detector, which are obtained in the measurement step, in an evaluation formula (f i) based on a circle equation in which the center coordinates of the calibration gauge are (x c, z c) and a radius of the calibration gauge is r; and a calibration step for calibrating a gain (g) for converting the first displacement (z i) of the point on the arm in the z-direction detected by the second detector into a second displacement of the tip of the contact point in the z-direction, and each parameter included in the deviation (dx, dz) based on the results obtained in the assignment step, wherein the evaluation formula (f i) in the assignment step is determined based on: an arm reference length as a length from the base point to a reference point as a foot of a perpendicular line extended from the tip of the contact point to a base line extending in longitudinal direction of a base shaft of the arm; a detection value (x i) of the first detector; the first displacement (z i); the gain (g); and a tip compensation amount (h) as a length from the reference point to the tip of the contact point, and wherein, with the known arm reference length being given, the center coordinates (x c, z c), the radius (r), the gain (g), and the tip compensation amount (h) are found in the calibration step.