Provided are an internal olefin sulfonate composition which is capable of sufficiently enhancing foamability, foam dissipation property free from a slimy feeling during rinsing, and a feel after cleansing and subsequent drying, and a cleansing composition containing the same.The internal olefin sulfonate composition comprises (A) an internal olefin sulfonate having 16 carbon atoms and (B) an internal olefin sulfonate having 12 carbon atoms, in which a content mass ratio of the component (A) to the component (B), (A/B), is from 10/90 to 90/10.