Each of a plurality of reels is provided with a plurality of symbols including at least one special symbol. At least one payline is extending across the reels. At least one electro-optical panel includes a first transparent substrate and a second transparent substrate which sandwiches an electro-optical substance therebetween. At least one of the first transparent substrate and the second transparent substrate is formed with at least one bored portion having a shape substantially coincident with an contour of the special symbol, the electro-optical panel disposed in front of each of the reels such that the bored portion is placed on the payline. A controller controls a state of the electro-optical substance in accordance with a predetermined rule to adjust a transparency of the electro-optical panel.