Patent ID: 7928350

Claim:
A microwave heating apparatus for radiating a microwave oscillated from a magnetron to a heating chamber via a waveguide, wherein a plurality of electricity feeding ports for radiating the microwave are provided at a ceiling wall of the heating chamber, and the wave guide is formed in an L-like shape including a side waveguide extended upwardly along an outer side face of the heating chamber such that the side waveguide is in direct contact with the outer side face of the heating chamber and an upper waveguide extended from an upper end of the side wave guide along an outer face of the ceiling wall to an end portion opposed to the upper end of the side waveguide, wherein the upper waveguide has opposing front and rear waveguide walls extended from the upper end of the side waveguide to the end portion of the upper waveguide, wherein the plurality of electricity feeding ports are formed by at least two or more kinds of electricity feeding ports having different shapes and opening areas, wherein when the plurality of electricity feeding ports are aligned in a front and rear direction of the ceiling wall, the opening area of the electricity feeding port at a position proximate to a center of the ceiling wall is set to be larger than the opening area of the electricity feeding port at a position remote from the center of the ceiling wall, and the opening area of the electricity feeding port at a position proximate to the center of the ceiling wall reaches the end portion of the upper waveguide and a corner of the upper waveguide, and the opening area of the electricity feeding port at a position remote from the center of the ceiling wall reaches the end portion of the upper waveguide and does not reach the rear waveguide wall, wherein a distance between an antenna of the magnetron and a center of the opening area of each of the electricity feeding port at a position proximate to the center of the ceiling wall and the electricity feeding port at a position remote from the center of the ceiling wall is g/2 multiplied by an integer, wherein g is a wavelength of the microwave propagated at an inside of the waveguides, and wherein an inclined face is formed at a connecting portion between the upper waveguide and the side waveguide.