A method for evaluating the refractive index homogeneity of an optical member includes passing light through an optical member (1) used for photolithography. The side surface (1a) with respect to the optical axis (AX) of the optical member (1) is retained by elastic members (4) at a plurality of positions disposed at equal intervals to pass light through the optical member (1) and measure a wave front aberration. The optical member is rotated around the optical axis (AX) by the equal interval to measure a wave front aberration again and determine the difference from the initial measurement. The optical member (1) is moved in a direction perpendicular to the optical axis (AX) to measure a wave front aberration again and determined the difference from the initial measurement. The refractive index homogeneity of the optical member can be accurately evaluated from those differences by using fitting of the Zernike cylindrical function.