PURPOSE: To improve the surface active agent concentration and transparency of solution by mixing a mixture of an anionic surface active agent and a specified cationic surface active agent with water.

CONSTITUTION: (a) An anionic surface active agent of, preferably, sulfonate, sulfate or carboxylate type (e.g.: a 13-17C sodium alkane sulfonate) and (b) a cationic surface active agent with a mole ratio of a:b=1:30 to 0.3-10, which is a quaternary ammonium salt of the formula (R1 and R2 are each 1-4C alkyl, or oxyalkylene having 1-10 ethyleneoxide units and/or propyleneoxide units; R3 is 6-12C alkyl or alkenyl; R4 is R3 or benzyl; X- is cation of inorganic or organic acid) are mixed to obtain a mixture (B). (A) Water; 15-70 wt.% is mixed with the B component; 30-85 wt.% at 25-95°C, preferably, 40-85°C for 5-50 minutes.