A doubly-imaging fiber-lens (DIF) was fabricated by the photocopolymerization of methyl methacrylate with vinyl benzoate. The core and the outer portions of the DIF have the quadratic refractive-index distributions with different gradient-indexes from one another. The DIF forms two images different both in reduction rate and in image plane. Tracings of rays through DIF, assuming a meridional ray under paraxial condition, led to a simple and feasible method estimating the indexprofile of DIF on a basis of its lens function. The validity of this method was verified by the measurements in various conditions and the comparison with the index-profile determined interferometrically.