To conveniently and safely prevent adhesion of a cooked food such as a fish or the like to a grill.

The food F to be cooked such as the fish is placed on a first grill 11a, and a second grill 11b is preheated at the early stage of igniting grill burners 9, 10. And, some time after ignition, the second grill 11b completes preheating, and is raised upward by a thermally actuated spring 18, and thus the grill for placing the food F to be cooked is switched from the first grill 11a to the second grill 11b. Accordingly, preheating of the grill can be automatically done merely by first storing the food F to be cooked in a grill chamber 8 and igniting the grill burners 9, 10. Therefore, adhesion of the cooked food F such as the fish to the grill can be conveniently and safely prevented.