An apparatus for measuring a thickness of a lens is disclosed. The apparatus includes a first support, a second support, a third support, a first positioning element, a second element and a measuring element. The lens is disposed on the third support. The first positioning element is fixed to the first support to press against a first face of the lens beforehand. The second positioning element is movably mounted to the second support. The second positioning element can move towards the lens to press against a second face of the lens. The measuring element calculates the thickness of the lens according to the moving distance of the second positioning element.