A sulfur dioxide absorbent that is an ionic liquid including a solvent; and a salt of a diamine compound that is substituted with a hydroxyl group and has a chemical formula 1 to 3 below dissolved in the solvent: where, in Chemical Formula 1 and 2, R1-R4 are the same or different and each is independently selected from the group consisting of H, a C1-C6 alkyl, and a C1-C6 alkoxy; and where, in Chemical Formula 1 to 3, X is selected from the group consisting of Cl, Br, I, MeSO3, CF3SO3, HCO2, CF3CO2 and CH3CO2; and n is an integer of 1-10. The sulfur dioxide absorbent is constituted to selectively absorb sulfur dioxide and sulfurous acid (H2SO3) formed by combination of sulfur dioxide with water, not CO2.