NOVELTY - A gas cleanup apparatus (10A) has apparatus (12) for reducing temperature of high-temperature gas (11) containing sulfur and hydrogen cyanide components, desulfurizing agent supply apparatus (15), hydrogen cyanide removal agent supply apparatus (32), membrane filter and dust collector (16). The membrane filter collects dust contained in gas. The dust collector forms a composite deposit of desulfurizing agent and hydrogen cyanide removal agent to the surface of membrane filter.    USE - For gasification system and gasification power generation system (both claimed), and for removing sulfur component and hydrogen cyanide compound from gas obtained by gasifying biomass.    ADVANTAGE - The apparatus stably enables removal of hydrogen sulfide and hydrogen cyanide. Acidic gas contained in to-be-processed gas is effectively removed.    DETAILED DESCRIPTION - A gas cleanup apparatus (10A) has a gas-cooling apparatus (12) for reducing temperature of high-temperature gas (11) containing at least a sulfur component and hydrogen cyanide component, a desulfurizing agent supply apparatus (15), hydrogen cyanide removal agent supply apparatus (32), a membrane filter and dust collector (16). The apparatus (15) supplies powder-form desulfurizing agent (14) into coolant gas (13), which is temperature-reduced by apparatus (12). The apparatus (32) supplies powder-form hydrogen cyanide removal agent (31) into temperature-reduced gas. The membrane filter collects dust contained in gas. The dust collector forms a composite deposit of desulfurizing agent and hydrogen cyanide removal agent to the surface of membrane filter. INDEPENDENT CLAIMS are included for the following:    (1) gasification system, which has the gas cleanup apparatus; and    (2) gasification power generation system, which has the gas cleanup apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic view of gas cleanup apparatus. (Drawing includes non-English language text)    Gas cleanup apparatus (10A)    High-temperature gas (11)    Gas-cooling apparatus (12)    Cooling gas (13)    Desulfurizing agent (14)    Desulfurizing agent supply apparatus (15)    Hydrogen cyanide removal agent (31)    Hydrogen cyanide removal agent supply apparatus (32)