In this paper we propose a method for measuring the negative refraction index of films of optically transparent materials. The method is based on recording the direction of propagation and the shifting of the ray reflected from the film. It is shown that the method can be applied for both macroscopic and nanometric samples. However, a precise control of parameters of the radiation source is needed for using this method in the case of nanometric samples. The conditions for a composite medium to acquire a negative refractive index are discussed.