Surgery can become safer and more reliable if the conditions of the organs can be physically and quantitatively assessed through simultaneous intraoperative measurements and physical estimations of deformed organs. This study proposes a new method for estimating external forces based on local displacement of elastic bodies. Using this method, one can estimate the magnitude and position of forces not only on the forceps but also in the invisible field. Simulation studies confirmed the effectiveness of this method. The experimental results showed that partial observation of a deformed shape achieved successful estimation of the external forces.