1. A computer simulation method for a macromolecular material comprising: a process in which a coarse-grained model of a macromolecular chain modeled by a plurality of beads is defined, a process in which, using the coarse-grained model disposed in a predetermined virtual space, a molecular dynamics calculation is performed, a first calculation process in which a Rouse parameter of the coarse-grained model are computed, a process in which, an all-atom model of an arbitrary macromolecular chain modeled by a plurality of particle models of respective atoms is defined, a process in which, using the all-atom model disposed in a predetermined virtual space, a molecular dynamics calculation is performed by the computer, a second calculation process in which a Rouse parameter of the all-atom model are computed, a convert process in which, using the obtained Rouse parameter of the coarse-grained model and the obtained Rouse parameter of the all-atom model, a unit system employed in the molecular dynamics calculation performed by the use of the coarse-grained model is converted into a unit system employed in the macromolecular chain, wherein the second calculation process comprises an entire-length calculation process for obtaining the entire length of the all-atom model, and the entire-length calculation process comprises a process in which the position of a carbon atom of the all-atom model at one end thereof is fixed relatively to the virtual space, a process in which a carbon atom of the all-atom model at the other end thereof is forced to move away from said one end, while performing the molecular dynamics calculation, so that the all-atom model is forcibly stretched, a process in which the forcibly stretched all-atom model is structurally stabilized by performing a calculation according to a molecular mechanics method, and a process in which the distance between said one end and other end of the all-atom model structurally stabilized is computed as the entire length Lf of the all-atom model.