A method and apparatus for measuring refractive index of an object are disclosed. The method includes, acquiring a number of first fringes of a first interference pattern formed by interference of a first beam of light transmitted through the object with a second beam of light not transmitted through the object; acquiring a number of second fringes of a second interference pattern formed by interference of a third beam of light reflected from a first surface of the object with a fourth beam of light transmitted through the object and reflected from a second surface of the object; and calculating the refractive index of the object based on the number of first fringes and the number of second fringes. The method may further include calculating the Abbe number of the object based on the refractive indices of the object measured at different wavelengths.