The utility model discloses an air conditioner, which mainly comprises a draught fan and a motor, wherein the motor is mounted in an auxiliary mounting system and connected with the draught fan through a transmission belt, and an automatic adjusting device capable of adjusting height is arranged at the bottom of the motor and connected with the inner wall of the auxiliary mounting system. On the basis, the air conditioner solves the problems of the prior art that the transmission belt is easy to loosen, which leads to the transmission efficiency reduction and the flutter of the motor, so as to ensure that the transmission belt is permanently tensioned and effectively buffer the fluttering of the motor.