To quickly adjust devices by facilitating the operation of locking or unlocking the front door.

The upper right part of a front door 12 of a slot machine 10 is formed thick enough to allow the mounting of a key cylinder the same as that mounted on a key operation part of front doors of other game machines such as pachinko machines and a key operation part 20 is mounted to unlock the front door 12. As a result, the front door 12 can be unlocked using the same key as those of other game machines while the key can be inserted into the key operation part 20 simply by making hands extend firm in standing positions without stooping when the slot machine 10 is installed at game parlors together with other game machines. This facilitates the locking or unlocking of the front door thereby speeding up the adjustment of the slot machine 10.