We propose a new method that is enable to deform a soft object with Finite Element Method in real-time processing. The proposed method has a feature that the object is constraint in a contact point. When the contact point is changed, the inverse matrix of the rigid one is also changed. Since the calculation amount of the inverse matrix is O(n^3), the real-time processing is impossible. In the proposed technique, the calculation amount is reduced to O(n). So in the experiments, we checked its usefulness.