Disclosed is a measuring method which can measure the decentering of an axis by the measurement of a two-dimensional curved surface profile. This method has a first step of measuring a profile of a examined surface by a probe from a first reference position which is a position separate by a predetermined amount from a predetermined position on the examined surface of a subject lens, a second step of measuring the profile of the examined surface by scanning the examined surface by the probe from the second reference position which is a position separate by a predetermined amount from said predetermined position in a route opposite to the scanning direction of said first step after a rotation of the subject lens; and the step of obtaining the decentering amount of the examined surface by the use of the measurement results obtained at the first and second steps.