Players input their messages in their video game apparatuses and the messages are once collected at a server apparatus, thereafter they are distributed to all video game apparatuses from the game server apparatus. In a display screen of each video game apparatus, a chat window is displayed in order to display messages exchanged between the players on a game screen including a field and characters of the game. The chat window is sequentially enlarged up to a preset maximum number of lines when a new message is received from the game server apparatus. The chat window is sequentially reduced to the preset minimum number of lines when a predetermined time passes without any reception of new message or when the player performs a specific operation.