To provide a solubilizing process by which an anionic surfactant and a cationic surfactant can be uniformly solubilized without losing their effects as surfactants and to provide a solubilized solution obtained by it and a liquid detergent composition using it.

A transparent and uniform solubilized solution is obtained by adding an anionic surfactant (b) and a cationic surfactant (c) to a liquid (a) comprising water or water and an aqueous solvent and stirring it in the presence of a solubilizing agent (d). As the solubilizing agent (d), a carboxylic acid salt selected from the group consisting of an aliphatic dicarboxylic acid salt having a 7-16C alkyl or alkenyl group and a 7-12C aliphatic carboxylic acid salt is used.