To provide a lens refractive index measuring method capable of measuring easily and inexpensively a refractive index of a lens.

In this measuring method using a lens meter capable of measuring a dioptic power of the lens, the examined lens L is arranged on a nose piece 9 serving as a measuring base point of the lens meter, and the first dioptic power of the lens is measured in the atmospheric air. Then, the lens L provided respectively with the first and second transparent gel bodies 16, 21 of the same material brought into close contact with close contact faces 18, 23 on obverse and reverse face sides of the examined lens L are arranged on the nose piece 9 to measure the second lens dioptic power of the examined lens L sandwiched with the both gel bodies 16, 21, in the atmospheric air. The refractive index of the examined lens L is calculated based on the obtained first and second lens dioptic power.