In order to produce sulfites from SO(2) contained in flue gases, an SO(2) absorption experiment was conducted using a gas mixture with oxygen that emulates industrial flue gases. Concentrations of sulfite and sulfate produced by SO(2) absorption were measured, and their production ratios were assessed at a temperature of 303 K. The major product was sulfate when SO(2) was absorbed at a pH of 6.5 or below 4. When the pH of the liquid absorbent was around 4, the major product was sulfite. The production ratio of sulfite can thus be controlled using the pH of the liquid absorbent.