To provide a hinge mechanism of a game machine, which prevents a fraud, such as forming a gap between frames, while disposing a hinge pin so as to be vertically moved.

The hinge mechanism 3a of a Pachinko machine includes: a vertically movable hinge pin 30; and a plate-like member 3b provided with a pin hole to be engaged with the hinge pin 30. The hinge pin 30 has an engagement abut part 32 extending horizontally to be brought into vertically contact with a vertical movement regulating piece 70 formed on a glass door 5. The hinge pin 30 is fitted to a turning position where the engagement abut part 32 deviates from the position vertically opposite to the vertical movement regulating piece 70 to move vertically, and a turning position where the engagement abut part 32 is located vertically opposite to the vertical movement regulating piece 70 and the engagement abut part 32 abuts on the vertical movement regulating piece 70 to regulate vertical movement. The mechanism includes a pin lock member 40 engaged with the engagement abut part 32 to hold the hinge pin 30 in the turning position that regulates vertical movement.