A surface-profile measuring instrument, comprising: a scanning probe including a probe to be moved toward or contacted with a workpiece surface with an arc portion on at least a part thereof, the scanning probe scanning the workpiece surface while keeping the relative position between the probe and the workpiece surface at a predetermined reference position; a scanning vector commanding unit that is adapted to command a scanning vector command indicating a next movement position of the scanning probe along the workpiece surface; a drive mechanism having a drive shaft that is adapted to hold and three-dimensionally move the scanning probe in accordance with the scanning vector command; a drive sensor that is adapted to detect a drive amount of the drive mechanism; a movement-estimating unit that is adapted to estimate a movement condition of the drive mechanism based on the scanning vector command issued by the scanning vector commanding unit to calculate an estimated movement state quantity; and a correction calculating unit that is adapted to calculate a detection value of the drive sensor, wherein movement-estimating unit includes: a nominal-model setting unit that is set with a nominal model of a frequency transfer characteristics from the issuance of the scanning vector command from the scanning vector commanding unit until the command is reflected to the movement position of the scanning probe; a position-estimating unit that is adapted to acquire the position of the scanning probe as an estimated position using the scanning vector command from the scanning vector commanding unit and the nominal model set in the nominal-model setting unit; and a second-order differentiating unit that is adapted to second-order differentiate the estimated position of the scanning probe acquired by the position-estimating unit to calculate the acceleration as the estimated movement state quantity, and wherein the correction calculating unit is adapted to calculate a correction-amount for correcting a measurement error generated by a deformation of the drive mechanism in accordance with the movement thereof based on the estimated movement state quantity. a scanning probe including a probe to be moved toward or contacted with a workpiece surface with an arc portion on at least a part thereof, the scanning probe scanning the workpiece surface while keeping the relative position between the probe and the workpiece surface at a predetermined reference position; a scanning vector commanding unit that is adapted to command a scanning vector command indicating a next movement position of the scanning probe along the workpiece surface; a drive mechanism having a drive shaft that is adapted to hold and three-dimensionally move the scanning probe in accordance with the scanning vector command; a drive sensor that is adapted to detect a drive amount of the drive mechanism; a movement-estimating unit that is adapted to estimate a movement condition of the drive mechanism based on the scanning vector command issued by the scanning vector commanding unit to calculate an estimated movement state quantity; and a correction calculating unit that is adapted to calculate a detection value of the drive sensor, wherein movement-estimating unit includes: a nominal-model setting unit that is set with a nominal model of a frequency transfer characteristics from the issuance of the scanning vector command from the scanning vector commanding unit until the command is reflected to the movement position of the scanning probe; a position-estimating unit that is adapted to acquire the position of the scanning probe as an estimated position using the scanning vector command from the scanning vector commanding unit and the nominal model set in the nominal-model setting unit; and a second-order differentiating unit that is adapted to second-order differentiate the estimated position of the scanning probe acquired by the position-estimating unit to calculate the acceleration as the estimated movement state quantity, and wherein the correction calculating unit is adapted to calculate a correction-amount for correcting a measurement error generated by a deformation of the drive mechanism in accordance with the movement thereof based on the estimated movement state quantity. a nominal-model setting unit that is set with a nominal model of a frequency transfer characteristics from the issuance of the scanning vector command from the scanning vector commanding unit until the command is reflected to the movement position of the scanning probe; a position-estimating unit that is adapted to acquire the position of the scanning probe as an estimated position using the scanning vector command from the scanning vector commanding unit and the nominal model set in the nominal-model setting unit; and a second-order differentiating unit that is adapted to second-order differentiate the estimated position of the scanning probe acquired by the position-estimating unit to calculate the acceleration as the estimated movement state quantity, and wherein the correction calculating unit is adapted to calculate a correction-amount for correcting a measurement error generated by a deformation of the drive mechanism in accordance with the movement thereof based on the estimated movement state quantity.