A surface shape of a member to be measured is measured by reflecting measuring light at a reflection surface of a probe and utilizing an atomic force exerting between the probe and utilizing an atomic force exerting between the probe and the member to be measured. In addition to a first scanner for driving the probe, a second scanner for moving a focus position of an optical system is provided. Position conversion data representing a correlation between amounts of control of the first scanner and the second scanner are obtained in advance. By synchronously driving the first scanner and the second scanner, the focus position of the optical system is caused to follow the probe to improve measurement accuracy.