PURPOSE: To prevent irregular heating or lack of heating or over-heating from being produced in reference to a shape or a kind of cooked items and further to enable their cooking to be well carried out.

CONSTITUTION: An upper opening 7 and a lower opening 8 for supplying microwave from a magnetron 12 are arranged at each of upper location and lower location within a heating and cooking chamber. An upper closing plate 13 and a lower closing plate 14 for use in opening or closing each of the openings 7 and 8 are pivotally supported at edges of these upper opening 7 and the lower opening 8. There is provided one closing plate driving motor 17 for rotationally driving these upper closing plate 13 and lower closing plate 14 through a cooperative driving means 25. When the upper opening 7 is released under an operation of the cooperative driving means 25, the lower opening 8 is closed and in turn when the upper opening 7 is closed, each of the closing plates 13 and 14 is cooperatively driven in such a manner that the lower opening 8 is released.