To provide a ball tank of a game machine capable of smoothly sending out balls without causing ball clogging.

In the ball tank 1 of the game machine for sending out the balls to a ball aligning rail 2, the side walls 13a and 13b of the ball tank 1 parallel with a ball flow-down direction are unevenly narrowed from both sides and connected to a downstream end side wall 18. A recessed groove 15 for aligning the balls in one line and sending them out to the downstream is provided on the bottom surface 11 of the ball tank 1, a curve part 17 is formed at a part where the recessed groove 15 is connected to the bottom surface 11 of the ball tank 1, and the flow-down of the balls is accelerated. Also, an inclined surface 14 inclined oppositely to the ball flow-down direction is provided on the downstream side end part of the ball tank 1, and a ball pressure applied to the downstream end side wall 18 is suppressed.