Abstract: A microwave oven includes a heating chamber, a plurality of cooking utensils detachably disposed in the heating chamber selectively in accordance with the cooking contents, a plurality of heat sources heating food placed on or contained in the cooking utensil and including a magnetron, an oven heater and a grill heater, optical sensors determining the cooking utensil disposed in the heating chamber, and a microcomputer. The cooking utensils include a glass dish, thawing gridiron, pot, upper and lower top plates, one-legged top plate, and gridiron. A microwave cooking mode is selected when the determination of the optical sensors indicates that neither upper nor lower top plate is present in the heating chamber. A heater cooking mode is selected when either upper or top plate is present. When the heater cooking mode is selected on the basis of presence of the upper top plate, either an oven mode or a grill mode is selected depending upon presence or absence of the gridiron.