A network game system of high interest in which a contingency and/or unpredictability intervenes in a data exchange between players in a network game is provided. When a map item and a character are selected, a game apparatus transmits a data exchange request and character information to a server apparatus. The received character information is stored in a character management table of the server apparatus. When a predetermined time elapses after the data exchange request, other-character information is specified, and the character management table is updated. The other-character information is transmitted to the game apparatus, and the game apparatus updates each table based on the received information.