Disclosed is a microwave oven having a tray which is arranged in a cooking chamber and on which a food to be cooked or a vessel having accommodated therein a food to be cooked is placed and a tray driving section which is disposed in a driving chamber for transferring rotating force to the tray. The microwave oven includes a tray supporting unit for preventing the tray from being released from an original installation position. The tray supporting unit includes a first coupling portion which is formed on a driving shaft of the tray driving section, a second coupling portion which is press-fitted around the first coupling portion, and supporting arm portions which extend from the second coupling portion in a radial direction so as to be respectively engaged with an edge of the tray.