Solution properties of sodium 1-oxo-1-[(4-fluoroalkyl)phenyl]-2-alkanesulfonates, hybrid surfactants containing a fluorocarbon chain and a hypercarbon chain in the molecule, have been measured in terms of Krafft point, surface tension, n-octane/water and water/perfluoro-n-hexane interfacial tension, and aggregation number of micelles. The Krafft point, the area occupied by a molecule at the air/water and octane/water interfaces, and the aggregation number of micelles increase with an increase of fluorocarbon and/or hydrocarbon chain length, while critical micelle concentration (cmc), surface tension, and octane/water interfacial tension at the cmc decrease with an increase of fluorocarbon and/or hydrocarbon chain length. These surfactants are found to exhibit lower surface tension and hydrocarbon/water and fluorocarbon/water interfacial tension at the same time and make it possible to float a surfactant aqueous solution on a hydrocarbon substance such as benzene.