The present invention provides a method for collecting waste heat of exhaust gas and reducing white smoke, and an apparatus to which the method can be easily applied, the method comprising the steps of: introducing exhaust gas from an exhaust gas supply source including high-temperature steam to a heat and moisture exchange unit, collecting latent heat of the steam contained in the exhaust gas by making contact between the exhaust gas and a solution containing hydroscopic salts, condensing the collected latent heat, and discharging the processed exhaust gas to the outside of the heat and moisture exchange unit; and concentrating, cooling, and circulating the solution containing the hydroscopic salts by discharging, to a lower part of the heat and moisture exchange unit, a mixture of the solution containing the hydroscopic salts and condensation water.