An air conditioner includes a control box assembly capable of efficiently utilizing a space inside a control box and easily performing inspection and repair of a circuit unit disposed in the control box. The air conditioner includes a case that constitutes an exterior and a control box assembly mounted in the case, wherein the control box assembly includes a control box in which an accommodation portion is formed, a sliding panel having one side on which a circuit unit is mounted and being accommodated in the accommodation portion so as to be taken out of the control box, and a rotation panel having one side on which the circuit unit is mounted and being rotatably mounted at one side of the control box.