PURPOSE: To enable irregular heating at a plane-like cooked item or dispersed type cooked item to be eliminated by a method wherein supplying ports for supplying microwave into a cooking chamber are arranged at an upper part and a lower part of a side wall of the cooking chamber, respectively.

CONSTITUTION: Supplying ports 14 and 15 for supplying microwave into a cooking chamber 2 are arranged at each of an upper part and a lower part of a side wall 2a of a cooking chamber. Microwave is supplied from each of an upper part and a lower part of the side wall 2a, respectively. When the microwave is supplied from the upper part of the side wall 2a of the cooking chamber, the central part of a bottom part within the cooking chamber 2 is heated in a relative high degree and in turn when microwave is supplied from the lower part of the side wall 2a, an intermediate part and a circumferential part at the bottom part within the cooking chamber 2 are heated in a relative high intensity. Accordingly, in the case that the cooked items are arranged in a planer form or in dispersed state, microwave is supplied from both upper supplying port 14 and lower supplying port 15 under an operation of the microwave supplying control means. Due to this fact, the central part and the circumferential part of the cooked item are uniformly heated and then a cooking having no irregular heating can be carried out.