PURPOSE: To cook food excellently, by disposing an infrared-ray sensor unit at a marginal position of the top plate not influenced by the radiant heat of an oven lamp, and thereby detecting the infrared rays emitted from the food to be cooked in the oven correctly.

CONSTITUTION: A socket 13 for an oven lamp 12 is provided at a portion of the top plate 6a of an oven frame 6 incorporating therein a tray or trays, and an infrared-ray sensor unit 21 having a measurement port 20 is fixed to a marginal position of the top plate 6a not influenced by the radiant heat of the oven lamp 12, in the manner that it is directed toward the central portion of the tray in the oven. The infrared-ray sensor unit 21 comprises an inclined base plate 23 disposed in a case 22 and an incident-ray guide sleeve 25 fixed to the base plate 23 together with an infrared-ray sensor element 24. Here, the element 24 is positioned such that it faces the food to be cooked on the tray through the port 20. With such an arrangement, infrared rays emitted from the food at the time of cooking the same are passed through the port 20 and received and measured by the element 24, and the output of a magnetron 11 is controlled by the output signal of the sensor unit 21.