A surfactant composition, comprising a micelle or a vesicle, wherein the micelle or vesicle contains surfactin represented by the following formula (I): wherein 'X' is a residue of an amino acid selected from leucine, isoleucine and valine; and R 1 is a C 9-18 alkyl group, and a cationic surfactant having two C 8-20 alkyl groups or a cationic surfactant having one C 8-20 alkyl group, wherein the molar ratio of the cationic surfactant having two C 8-20 alkyl groups or cationic surfactant having one C 8-20 alkyl group to the surfactin (I) is not less than 0.8 and not more than 1.2, wherein the cationic surfactant having two C 8-20 alkyl groups is represented by the following formula (II): wherein R 2 and R 3 are independently C 8-20 alkyl groups; R 4 and R 5 are independently C 1-4 alkyl groups; and R 4 and R 5 may bind to one another to form a ring, and wherein the cationic surfactant having one C 8-20 alkyl group is represented by the following formula (III) or (IV): wherein R 6 is a C 8-20 alkyl group; each of R 7 , R 8 and R 9 is independently a C 1-4 alkyl group; R 10 is a C 8-20 alkyl group; and two of R 7 to R 9 may bind to one another to form a ring. comprising a micelle or a vesicle, wherein the micelle or vesicle contains surfactin represented by the following formula (I): wherein 'X' is a residue of an amino acid selected from leucine, isoleucine and valine; and R 1 is a C 9-18 alkyl group, and a cationic surfactant having two C 8-20 alkyl groups or a cationic surfactant having one C 8-20 alkyl group, wherein the molar ratio of the cationic surfactant having two C 8-20 alkyl groups or cationic surfactant having one C 8-20 alkyl group to the surfactin (I) is not less than 0.8 and not more than 1.2, wherein the cationic surfactant having two C 8-20 alkyl groups is represented by the following formula (II): wherein R 2 and R 3 are independently C 8-20 alkyl groups; R 4 and R 5 are independently C 1-4 alkyl groups; and R 4 and R 5 may bind to one another to form a ring, and wherein the cationic surfactant having one C 8-20 alkyl group is represented by the following formula (III) or (IV): wherein R 6 is a C 8-20 alkyl group; each of R 7 , R 8 and R 9 is independently a C 1-4 alkyl group; R 10 is a C 8-20 alkyl group; and two of R 7 to R 9 may bind to one another to form a ring. wherein 'X' is a residue of an amino acid selected from leucine, isoleucine and valine; and R 1 is a C 9-18 alkyl group, and a cationic surfactant having two C 8-20 alkyl groups or a cationic surfactant having one C 8-20 alkyl group, wherein the molar ratio of the cationic surfactant having two C 8-20 alkyl groups or cationic surfactant having one C 8-20 alkyl group to the surfactin (I) is not less than 0.8 and not more than 1.2, wherein the cationic surfactant having two C 8-20 alkyl groups is represented by the following formula (II): wherein R 2 and R 3 are independently C 8-20 alkyl groups; R 4 and R 5 are independently C 1-4 alkyl groups; and R 4 and R 5 may bind to one another to form a ring, and wherein the cationic surfactant having one C 8-20 alkyl group is represented by the following formula (III) or (IV): wherein R 6 is a C 8-20 alkyl group; each of R 7 , R 8 and R 9 is independently a C 1-4 alkyl group; R 10 is a C 8-20 alkyl group; and two of R 7 to R 9 may bind to one another to form a ring. <EOS>