A pure chlorine dioxide solution includes a chlorine dioxide gas dissolved therein, a chlorite, and a pH adjuster which is an acid or a salt thereof having a buffering property whose pH is 2.5 to 6.8 as a 5% aqueous solution at 25°C.具有溶存二氧化氯氣體、亞氯酸鹽、及pH調整劑於構成成份,上述pH調整劑係於25℃時5%水溶液之pH成為2.5~6.8之具有緩衝性之酸或其鹽為特徵之純質二氧化氯液劑。