A door structure of a microwave oven usable as a pizza oven, wherein a pan is coupled to an inner surface of the door such that the pan is integral with the door, and a handle is mounted to an outer surface of the door. The handle has various structures so that the handle is separable from the door or is hingably mounted to the door to move between a folded state and an unfolded state. The door structure, may be configured to simultaneously open the door and eject the pan. The user can stably open and close the pizza oven door, using only a handle, under the condition in which the pizza oven door and pizza tray are not supported. The handle has a structure capable of effectively supporting the weight of the oven door while having a foldable structure so that the handle can be conveniently used.