1. A three-dimensional object processing device for executing processing for deforming a three-dimensional object that is disposed in a virtual three-dimensional space, comprising: projection means for projecting the three-dimensional object onto each of a plurality of projection planes that are set in the virtual three-dimensional space; projected object deformation means for deforming each of projected objects that are obtained by projecting the three-dimensional object onto each of the plurality of projection planes in a corresponding one of the plurality of projection planes; and three-dimensional object deformation means for deforming the three-dimensional object in the virtual three-dimensional space based on each of the projected objects, which have been deformed in the corresponding one of the plurality of projection planes.