Provided is an internal olefin sulfonate composition which is capable of exerting good foamability together with good volume of foam, foaming speed, foam dissipation property, foam quality, foam durability in the presence of sebum, and volume of foam in the presence of sebum at high levels, and a cleansing composition containing the same. The internal olefin sulfonate composition of the present invention comprises (A) an internal olefin sulfonate having 16 carbon atoms and/or (B) an internal olefin sulfonate having 18 carbon atoms, in which a total content of the component (A) and the component (B) is from 50 to 100% by mass, a content mass ratio (A/B) of the component (A) to the component (B) is from 0/100 to 70/30, a content of the internal olefin sulfonate in which a sulfonate group is present at a C-2 position is 25% by mass or less, and in which a mass ratio (hydroxy form/olefin form) of a content of a hydroxy form in the internal olefin sulfonate of the component (A) and the component (B) to a content of an olefin form in the internal olefin sulfonate of the component (A) and the component (B) is from 75/25 to 100/0.本發明提供一種可以高等級表現出良好之起泡性、泡量、速泡性、消泡性、泡質、皮脂存在下之泡之持續性、及皮脂存在下之泡量之內烯烴磺酸鹽組合物及含有其之洗淨劑組合物。本發明之內烯烴磺酸鹽組合物含有(A)碳數16之內烯烴磺酸鹽及/或(B)碳數18之內烯烴磺酸鹽，該成分(A)及成分(B)之合計含量為50~100質量%，且該成分(A)與成分(B)之含有質量比(A/B)為0/100~70/30，磺酸基存在於2位上之內烯烴磺酸鹽之含量為25質量%以下，並且成分(A)及成分(B)之內烯烴磺酸鹽中之羥基體之含量與成分(A)及成分(B)之內烯烴磺酸鹽中之烯烴體之含量之質量比(羥基體/烯烴體)為75/25~100/0。
