PURPOSE: To enable an automatic sensing of material quality of cooked item to be carried out to check if it is liquid such as milk and the like and further to improve its operating characteristic as well as its convenience in use in operation in it.

CONSTITUTION: Sensing microwave is oscillated from a microwave oscillation means 26 toward a cooked item 7. Microwave permeated through the cooked item 7 is received by a microwave receiving means 27. When a level of the received signal is lower than a reference value for judgement, material quality of the cooked item 7 is automatically judged as liquid. With such an arrangement as above, judgement of material quality of the cooked item 7 becomes accurate and at the same time its operating characteristic is improved. Then, since a control over supplying of microwave can be performed in response to a result of judgement, it is possible to eliminate an irregular heating when liquid such as milk and the like is heated.