To effectively perform a performance using light with a light intensity suitable for a changing illumination degree.

The game machine has a display control means (a CPU 31) for changing a screen display of a liquid crystal display 5 according to inside prize winning roles, an illumination degree detector 55 detecting the illumination degree outside, and a back light driving circuit 84 setting the light intensity of the display light of the liquid crystal display 5 by the display control means according to the illumination degree detected by the illumination degree detector.