Disclosed is an apparatus and a method for fumigation using chlorine dioxide. The apparatus for fumigation using chlorine dioxide includes: a supply part configured to supply the chlorine dioxide a gas sensor configured to sense the chlorine dioxide in a target space into which mixed gas including the chlorine dioxide is injected an introduction part configured to introduce dilution gas for diluting the chlorine dioxide a mixing part connected to the supply part and the introduction part, and configured to generate the mixed gas by mixing the dilution gas with the chlorine dioxide according to information on a concentration of the chlorine dioxide output from the gas sensor so that the concentration of the chlorine dioxide in the target space may be located within a preset actual concentration band and a transfer part connected to the mixing part to transfer the mixed gas to the target space.
