A gaming machine and a controlling method thereof are provided. The gaming machine includes a mechanical symbol display unit which includes: a rotatable reel having a peripheral face with a plurality of symbols thereon; an illuminating device that is provided within a space on an inner periphery side of the rotatable reel and is controlled to emit light of at least two different colors; and an illumination controller. The symbols include a special symbol having at least two translucent portions each having a unique color that is the same as one of the at least two different colors. The at least two colors are selected in a way that, the special symbol is observable as a symbol in one single color or a symbol with a pattern of at least two colors according to the color of the emitted light.