To provide a mechanism for supplying consistency, responsiveness and maintainability and enabling high reality in a distributed network simulation environment.

The consistency is achieved by executing the same arithmetic operation by using the same input in plural machines. The responsiveness is achieved by executing an arithmetic operation part for acting on the object of a user on the machine of the user earlier than the one for the object of the user on a server. The maintainability is achieved by dictatorially executing all the arithmetic operations on the server. The ability of making the different parts of a shared arithmetic operation run on the different machines at the different points of time is provided.