Provided are an internal olefin sulfonate composition which is capable of sufficiently enhancing foamability, light foam quality, and instantaneous foam dissipation property, and a cleansing composition containing the internal olefin sulfonate composition. The internal olefin sulfonate composition comprises (A) an internal olefin sulfonate having 12 carbon atoms and (B) an internal olefin sulfonate having 14 carbon atoms, wherein a content mass ratio of the component (A) to the component (B), (A/B), is from 10/90 to 90/10, and a total content of the component (A) and the component (B) in the internal olefin sulfonate is from 60 to 100% by mass.