To smoothly perform the virtual activity of a relevant participant when a terminal computer is connected to a central computer again even after the virtual activity processes or stops in the central computer while the virtual activity is separately performed in the state of temporarily disconnecting the terminal computer from the central computer.

Among terminal computers 21, 22 and 23 connected through a communication network 11 to a central computer 10, the terminal computer 21 is temporarily disconnected from the communication network 11. In this case, a virtual space/virtual time concerning the virtual activity cooperatively performed before is applied to a storage device 21d and the terminal computer 21 performs the virtual activity separately from the central computer 10. The local condition of the virtual space provided as a result is integrated into the central condition of the virtual space on the side of the central computer 10 in the case of new connecting to the central computer and the virtual activity to be newly cooperated is continued.