The invention relates to a microwave oven including a food-cooking enclosure, the electromagnetic energy of which is supplied by a set of two to four magnetrons (5, 6, 7) mounted on an enclosure wall, the magnetrons communicating with waveguides (55, 65, 75) which are in communication with the oven enclosure. The magnetrons are individually air-cooled and the air is then discharged to the outside via a discharge conduit.The invention is characterised in that the discharge conduits open out into a common calming chamber before discharge to the outside.