A progress-degree storage section (202) stores the degree of progress of a game. An input receiving section (203) receives the input of instruction operations. A game progressing section (204) causes the game to progress according to the instruction operations. A progress-degree update section (205) updates the degree of the progress in such a manner that the degree of the progress advances with the elapse of time from when the reception of input of an instruction operation is ended until the reception of input of the next instruction operation is started, and the difference between the degrees of progress stored in all terminal devices (201) becomes small and stops the update of the degree of the progress between the start and end of the reception of the input of the instruction operation. An image display section (206) displays an image of the game associated with the degree of the progress stored.