A flat display device includes a flat display module, a front cover supporting a front portion of the flat display module, a back cover supporting a rear portion of the flat display module, a peripheral portion formed on the back cover and having an inclined surface inclined toward a center of the flat display module as it goes rearward, and a cross-flow fan disposed in the back cover and aligned with the inclined surface of the peripheral portion of the back cover. The cross-flow fan has an air exhaust channel having an air outlet inclined toward the center of the flat display module as it goes rearward.