An air conditioner having an enhanced user perception and a controlling method thereof are provided. A predetermined character and/or its applied character image are/is displayed on a display window of the air conditioner. The character and/or the character image are/is changed depending on the operational states of the air conditioner, so that the user perceives the operational state of the air conditioner more conveniently. The air conditioner has advantages in that the user can perceive the operational state of the air conditioner more conveniently, the user can be stimulated to purchase the product, and a use term of the air conditioner can be extended.