PURPOSE: To facilitate operation of a device, by providing a supporting pipe having a sample holder attached to the upper end on the weight sensing tray of an electronic balance, and connecting the upper end of the protective pipe into which gaseous oxygen is introduced from the gas inlet of a gas feed ring with a suction pump.

CONSTITUTION: The gas feed ring 5 for feeding gaseous oxygen is placed on the upper plate of the electronic balance 3, an IR heating furnace 7 and the protective pipe surrounded with the furnace 7 are joined into one body and placed vertically movably on the ring 5. The supporting pipe 11 provided with the sample holder 12 at the upper end is installed on the weight sensing tray 3a of the electronic balance 3 in the pipe 8, and the upper end of the pipe 8 into which gaseous oxygen is fed from the gas outlet of the ring 5 is connected with the suction pump 24. The ash and sulfur contents contained in the sample is determined by connecting the furnace 7 to a temp. controller 2 capable of adjusting its temp. to that at which the combustible sulfur and incombustible sulfur are converted into gaseous sulfur dioxide, respectively.