To utilize generated thermal energy effectively by supplying animal or plant oil to an atmosphere preheated up to the thermal decomposition temperature thereof or above and thermally decomposing the animal or plant oil before being burnt.

An animal or plant oil combustor, i.e., a kitchen range 1, comprises a range body 3 and a tank 5, a torch burner 9, and a control board 11. When a starting switch on the control board 11 is turned on, a fan 33 is started to supply high pressure gas to a combustion chamber 19. A gas flow rate regulation valve 43 is then opened fully and high combustion takes place in the burner 9. When the temperature detected by a temperature sensor exceeds 600°C, the gas flow rate regulation valve 43 is restricted and the burner 9 is switched to low combustion. At the same time, waste animal or plant oil 27 is fed out from the tank 5. Consequently, the waste animal or plant oil 27 mixed with high pressure air is sprayed into a preheated container 15 where it is heated up to 600°C or above and burnt completely. After combustion is started, it is controlled to be held between 600-800°C in order to prevent overheat.