PURPOSE: To enable an operation of a heating device to be carried out by one operator and to save a labor for the operation by a method wherein a loading or un-loading port for use in loading or unloading a heated item into or out of a heating space within a cabinet and a conveyor for use in transporting the heated item is extended from the loading or unloading port to an external part.

CONSTITUTION: A cabinet 1 is provided with a heating space 2 within it. In addition, loading or unloading ports 3, 4 for use in loading or unloading a heated item 9 into or out of the heating space 2 are disposed in the same plane as that of an external part of a cabinet 1. Conveyors 5, 6 are extended from the loading or unloading ports 3, 4 out of these external portions in such a way that a handling of the heated item 9 is easily carried out by an operator. Leakage of micro-wave is prohibited by a micro-wave trap 10. The heated item 9 is transported to the cabinet port 4 from the cabinet port 3 through the heating space 2 disposed in the cabinet 1 by these conveyors 5, 6 and further during this transportation, a heating process is carried out within the heating space 2.