An outdoor unit of an air conditioner, according to an idea of the present disclosure, comprises: a housing; a fan which is disposed within the housing to move air; a machine room which is provided on one side of the fan; a first partition which is installed to define the machine room in the housing and includes an inlet hole provided to allow air discharged from the fan to be introduced into the machine room therethrough; a second partition which is installed to define the machine room in the housing and includes an outlet hole provided to allow air having cooled the machine room to be suctioned into the fan therethrough; a fan guard which is disposed in front of the fan and includes an opening provided at one side thereof facing the first partition to allow air discharged from the fan to flow toward the machine room therethrough; and a front cover which is disposed in front of the first partition to guide air having passed through the opening into the inlet hole.