To inhibit the detachment of a control board at the normal time such as during the business hours of a hall.

By inserting a locking lever of a main control board case 27 to the insertion hole of a main board attaching surface provided on the lower back surface side of a board attaching base 40, rotating it and attaining a locked state, the main control board case 27 is mounted to be long sideways. The board attaching base 40 has fitting parts 40a and 40b whose cross section is formed in a U shape so as to hold the left edge and right edge of a game board 30 from the front surface and the back surface on both left and right sides, the board attaching base 40 is slid from the lower direction to the upper direction of the game board 30 and mounted on the game board 30, and the game board 30 is fitted to the back surface side of the front surface frame of a pachinko game machine. In such a manner, since the main control board case 27 can not be detached unless the game board 30 is detached from the front surface frame, the detachment of the main control board case 27 at the normal time such as during the business hours of the hall is inhibited.