1. A method for tire rolling simulation on mud comprising the steps of: modeling a tire using finite elements to build a tire model; modeling a muddy road covered with mud using finite volumes to build a muddy road model which can exhibit elastoplasticity property, and failure property in which the finite volume fails under a certain tensile stress, but does not fail under any compression stress; and executing a numerical simulation in which the tire model is made to roll on the muddy road model in a predetermined condition.