NOVELTY - Raw-coal acid gas (AA) containing high-boiling-point and low-boiling-point type impurities is supplied to a liquid-carbon-dioxide fractionating column (101). Liquid carbon dioxide containing high-boiling-point type impurity is discharged out. Carbon dioxide gas discharged from the tower top is separated into flows (I,II). Flow (I) is condensed into liquid carbon dioxide. Flow (II) is mixed and low-boiling-point type impurity is separated.    USE - Removal of impurities in carbon-dioxide gas to be used in foodstuffs and medical applications.    ADVANTAGE - The method enables economical removal of both low-boiling-point type impurities and high-boiling-point type impurities, and provides product carbon dioxide gas with high recovery.    DETAILED DESCRIPTION - High-boiling-point type impurities having a boiling point higher than that of carbon dioxide gas, and low-boiling-point type impurities having a boiling point lower than that of carbon dioxide gas, contained in raw-coal acid gas are removed as follows. The raw-coal acid gas containing the impurities is supplied to a liquid-carbon-dioxide fractionating column, and a preset amount is guided to the tower top. Liquid carbon dioxide containing the high-boiling-point type impurity is discharged out of the system from the fractionating-column bottom and the impurities are removed. Carbon dioxide gas discharged from the tower top is separated into carbon-dioxide gas flow (I) with big flow volume and carbon-dioxide-gas flow (II) with small flow volume. Flow (I) is guided to a fractionating-column top condenser (105) and condensed to obtain liquid carbon dioxide. The liquid carbon dioxide is guided to a fractionating-column top gas-liquid separator (107). Flow (II) is mixed and low-boiling-point type impurity in liquid carbon dioxide is separated by the fractionating-column top gas-liquid separator with a re-flash, and the impurities are removed. An INDEPENDENT CLAIM is included for impurity-removal apparatus (100) consisting of a liquid-carbon-dioxide fractionating column, a fractionating-column top condenser, a fractionating-column top gas-liquid separator, and a purge line (115) which discharges the concentrated high-boiling-point type impurity.    DESCRIPTION OF DRAWING(S) - The drawing shows an explanatory view of the impurity removal apparatus. (Drawing includes non-English language text)    Impurity removal apparatus (100)    Liquid-carbon-dioxide fractionating column (101)    Fractionating-column top condenser (105)    Fractionating-column top gas-liquid separator (107)    Purge line (115)    Raw-coal acid gas (AA)