For tissue elasticity imaging, strain imaging technique is being used in clinical tests , However, strain image corresponds to visualizing the qualitative information about tissue hardness. Therefore, in this study, we propose a method for reconstructing tissue hardness as quantitatively as possible from ultrasound data using 1-D array ultrasonic probe. In this method, we use a modified 3-D finite-element model. Using this model, it becomes possible to estimate Young's modulus only from the 2-D strain distribution. Moreover, since we can use the more realistic 3-D elastic equations in the modified 3-D model, it is possible to estimate Young's modulus more quantitatively. We compared the performance of the proposed method with other methods based on the 1-D model, 2-D model and 3-D model. Consequently, although the proposed method is comparable to the 3-D model method in accuracy, this method has 4.0 times precision better than the 1-D model method, 3.0 to 1.5 times precision better than the 2-D model method. Moreover, the proposed method can attain high-speed processing about 170 times faster than the method using 3-D model.