A measuring method for an optical element for obtaining a plurality of measurement errors of the optical element is disclosed, which comprises steps of irradiating a laser ray to an overall portion of the optical element, wherein the optical element is supported as one of a horizontal state and a vertical state; rotating continuously the optical element with 360 degrees to reflect the laser ray to obtain a reflected light wavefront picture from the reflected laser ray; analyzing the reflected light wavefront picture to obtain a plurality of aberration characteristics information, respectively, each being one of a sine and a cosine wave functions of a wavefront error for each of the plurality of specified rotation angles; analyzing a plurality of interference factors each for the plurality of measurement errors on each of the plurality of aberration characteristics information, respectively; calculating and extracting a plurality of classified aberration characteristics information for each of the plurality of specified rotation angles of the optical element from each of the plurality of aberration characteristics information according to the plurality of measurement errors, respectively; and analyzing each of the plurality of classified aberration characteristics information to obtain an error amount corresponding to each of the plurality of measurement errors, respectively.