The invention provides a game system, a game machine, a game data distribution machine, a network system and an information storage medium whose clocks can be synchronized. The game system comprises a game data distribution machine having a master function and including a clock selection section for generating indication data for obtaining clock information and a transmitting/receiving section for transmitting the generated indication data and a game machine having a slave function and including a transmitting/receiving section for receiving the indication data sent from the game data distribution machine and a clock selection section for adjusting the clock speed of own machine so as to synchronize the clock of own machine with the clock of the game data distribution machine based on the received indication data.