To provide a mechanism board of a pachinko machine Capable of easily coping with an ordinary machine and a card-type pachinko machine.

In a mechanism board 5 of a pachinko machine comprising a winning ball discharger 12 for discharging a specific number of winning balls onto a ball supply tray on the basis of a winning ball detecting signal, at a downstream end of a guide passage 10 for aligning the Pachinko balls of a ball tank 9 to flow, a rental ball passage 40 is formed on the mechanism board 5, and a rental ball discharger for discharging a specific number of rental balls to a ball supply tray on the basis of a rental ball requirement signal is demountably mounted on the rental ball passage 40.