This application relates to an apparatus for reducing fine dust by using lightweight mixed air. The apparatus may include an apparatus main body configured to introduce and mix external air and remove the fine dust through adsorption, a seal type air mixing unit configured to mix the introduced external air and helium gas, an adsorption solution production unit configured to produce an adsorption solution for adsorbing the fine dust. The apparatus may also include an air bubble generation unit configured to generate air bubbles, emitted to outside, by using the adsorption solution, a flow control unit configured to control flow of air, so as to induce air bubble generation in the air bubble generation unit. The apparatus may further include a controller installed in a part of the apparatus main body and configured to control operations of the above units of the apparatus.