Provided is an outdoor unit of an air conditioner. The outdoor unit of the air conditioner includes a heat exchanger, a base arranged below the heat exchanger and including a first part including a drain hole formed to correspond to the heat exchanger to discharge water generated from the heat exchanger, and a second part formed to have a stepped portion with the first part, and a leg provided below the base and including a panel formed to slope while being spaced apart from the base such that the water is discharged through the drain hole.