An air conditioner including a door installed in order to provide a smooth appearance by hiding an outlet is provided. The air conditioner is installed on a wall and includes a front panel including a first panel part provided with an inlet and a second panel part connected to a lower portion of the first panel part and provided with an outlet; a lower panel connected to the second panel part of the front panel and extended toward the wall; and a door installed on a front surface of the second panel part so as to open and close the outlet while being slid, wherein the door is slid along a curved movement trajectory toward the lower panel, and a curvature of the movement trajectory is changed. A clean and smooth appearance may be formed using a door slid along a curved path and a slim appearance may be formed even in the state in which the door is opened.