To provide a game system capable of managing reliable information without increasing the cost of a game machine.

The game system has a card unit 15 (medium control unit) for reading and writing information recorded in a game card (storage medium), and a Pachinko machine 1 (game machine) capable of performing a game on the basis of the number of held balls (game value) that can increase in accordance with a reduction in a balance (valuable value) of the game card. The card unit 15 communicates with a game control device 54 of the Pachinko machine 1 to perform information management for suitably updating game information relating to a state of the Pachinko machine 1 and game value information relating to the number of held balls even during a game, and at least the game information can be output from the card unit 15 to a hall computer 86 or the like (external management device).