To appropriately respond to a sudden change in a supply amount of game media to a game medium use machine.

The game medium supply device 10 for use in a bank 1 of game machines, the bank being formed by aligning a plurality of game medium use machines 2 and 3, is provided with: a sloping guide passage 11a which conveys game media using a natural falling of the game media; a supply medium conveyance means 11 formed by alternately disposing medium transfer mechanisms 11b which deliver the game media from a conveying direction upstream side to a conveying direction downstream side; a conveying passage opening/closing means 13 openably/closably disposed in the conveyance-direction downstream end of the supply medium conveyance means 11 and communicating the supply medium conveyance means 11 to a game medium storage tank 5; and an operation control means 14 which controls the opening/closing operation of the conveyance passage opening/closing means 13 and executes the control based on information specifying the operation state of the game medium transfer mechanism 11b.