Multifingered robot hands have the ability to manipulate and grasp various objects, like a human hand. In previous studies, we have looked at paper folding operations (Origami) as an example of dexterous manipulation to be performed by dual robot hands. It is difficult for robot hands to manipulate a sheet of paper because of its deformation, and it is thus necessary to recognize its shape during Origami operations. In this paper, we propose a method of estimating a 3D model of paper based on depth information obtained from a 3D sensor. The 3D model of the paper is expressed by using a physics simulator composed of nodes with springs and dampers. As a result, highly accurate 3D shape estimation was achieved during Origami operations.