A digital object is manipulated by way of a physical object. As a digital space on a computer is deeply fused with a physical real space, it becomes possible to input user commands not only by way of native user input devices such as a mouse and a keyboard but also various physical objects that are scattered in the real world and draw out a digital object by way of a physical object. As a result, computers can be operated in a more intuitive and easy way and become attractive to the users.