NOVELTY - A microwave heating device consists of container (10), microwave generation apparatus, sample stand, port for introducing gas to inside the container, exhaust port (90) arranged facing the sample stand, gas detection apparatus for detecting gas concentration inhaled by exhaust port, calculator (130) which carries out process control based on result calculated by signal detected with a gas detection apparatus, and control controller (140) for controlling flow volume of gas introduced into container and measuring concentration of gas generated by microwave heating.    USE - Microwave heating device is used for removing impurity e.g. carbon from silicon mixed powder (claimed) used as silicon raw material for solar cell.    ADVANTAGE - The microwave heating device efficiently reduces carbon from the silicon mixed powder. The processed silicon material is recycled.    DETAILED DESCRIPTION - A microwave heating device consists of container, microwave generation apparatus for generating microwave inside the container, sample stand arranged inside the container stirs silicon mixed powder, port for introducing gas to inside the container, exhaust port arranged facing the sample stand, gas detection apparatus for detecting the gas concentration inhaled by the exhaust port, calculator which carries out a process control based on the result calculated by the signal detected with a gas detection apparatus, and control controller for controlling flow volume of the gas introduced into the container and measuring concentration of the gas generated by microwave heating. The microwave heating device irradiates microwave to silicon mixed powder obtained by mixing carbon in the silicon powder, and removes carbon from silicon. An INDEPENDENT CLAIM is included for method for removing impurity e.g. carbon from silicon mixed powder, which involves heating the silicon mixed powder in a container, generating gas, detecting generated gas, calculating signal, and controlling removal speed of carbon to specific range by controlling the gas volume introduced in the container.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of microwave heating device. (Drawing includes non-English language text)    Container (10)    Exhaust portion (90)    Gas analyzing apparatus (100)    Filter (110)    Calculator (130)    Control controller (140)