To provide a game ball prize-winning device which can be mounted easier in a narrow space as well with the minimized vertical dimensions of the body of the device by arranging a pivoted part at the lower part of an open/close door below the top surface of the prize-winning slot in a ball entry port.

The game ball prize-winning device A has a mounting plate 1 with the ball entry port 2 opened therein, the open/close door 18 which is pivoted at the lower part thereof and opens or closes the ball entry port 2 being turned longitudinally, prize-winning slots 7a and 7b which lead the pachinko balls B entering the ball entry port 2 to win it and a ball detector 8 which is disposed horizontally under the prize-winning slots 7a and 7b and detects the pachinko balls winning the prize-winning slots 7a and 7b. The pivoted parts 19 and 24 of the open/close door 18 are disposed below the top surfaces of the prize-winning slots 7a and 7b and guide parts 21 and 53a are so arranged on the rear side of the open/close door 18 to let the pachinko balls B be rolled to be smoothly sent into the ball entry port 2 as received on the top surfaces when the open/close door 18 is inclined forward.