An over-the-range microwave oven including a duct unit configured to direct air from the back of the oven to the front. The duct unit includes a first panel disposed between the housing and the cooking unit of the oven. The first panel forms a bottom wall of the duct unit. The duct unit further includes at least a pair of second panels disposed on both lateral sides of the first panel. The gap between the pair of second panels decreases from one side end toward the other side end.