To provide a network game function materializing method using a cellular phone enabling to play a game with a plurality of cellular phone users in materializing a game function in the cellular phone.

This method is characterized to be formed of a process designating a cellulose phone performing a network game, a process executing a network program of an own station according to a key signal for the network game inputted by a user, when the network game is started, transmitting game data corresponding to the inputted key signal for the network game to an opponent side portable telephone, receiving the game data from the opponent side, and executing the network game program of the own station cellular phone according to the changed data, and a process displaying the same game screen based on the game data changed at real-time on a display part of each cellular phone playing the network game.