A cationic lipid represented by formula: wherein: R 1 and R 2 are, the same or different, each linear or branched alkyl, alkenyl or alkynyl having 12 to 24 carbon atoms, or R 1 and R 2 are combined together to form dialkylmethylene, dialkenylmethylene, dialkynylmethylene or alkylalkenylmethylene, X 1 and X 2 are combined together to form a single bond or alkylene, X 3 and Y are absent, a and b are 0, L 3 is a single bond, R 3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidinyl or morpholinyl, and L 1 and L 2 are -O-, a and b are, the same or different, 0 to 3, and are not 0 at the same time, L 3 is a single bond, R 3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidinyl or morpholinyl, L 1 and L 2 are, the same or different, -O-, -CO-O- or -O-CO-, a and b are, the same or different, 0 to 3, L 3 is a single bond, R 3 is a hydrogen atom, and L 1 and L 2 are, the same or different, -O-, -COO or -O-CO-, or a and b are, the same or different, 0 to 3, L 3 is -CO- or -CO-O-, R 3 is pyrrolidin-2-yl, pyrrolidin-3-yl, piperidin-2-yl, piperidin-3-yl, piperidin-4-yl, morpholin-2-yl, morpholin-3-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, wherein at least one of the substituents is amino, monoalkylamino, dialkylamino, trialkylammonio, pyrrolidinyl, piperidyl or morpholinyl, and L 1 and L 2 are, the same or different, -O-, -CO-O- or -O-CO-. R 1 and R 2 are, the same or different, each linear or branched alkyl, alkenyl or alkynyl having 12 to 24 carbon atoms, or R 1 and R 2 are combined together to form dialkylmethylene, dialkenylmethylene, dialkynylmethylene or alkylalkenylmethylene, X 1 and X 2 are combined together to form a single bond or alkylene, X 3 and Y are absent, a and b are 0, L 3 is a single bond, R 3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidinyl or morpholinyl, and L 1 and L 2 are -O-, a and b are, the same or different, 0 to 3, and are not 0 at the same time, L 3 is a single bond, R 3 is alkyl having 1 to 6 carbon atoms, alkenyl having 3 to 6 carbon atoms, pyrrolidin-3-yl, piperidin-3-yl, piperidin-4-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidinyl or morpholinyl, L 1 and L 2 are, the same or different, -O-, -CO-O- or -O-CO-, a and b are, the same or different, 0 to 3, L 3 is a single bond, R 3 is a hydrogen atom, and L 1 and L 2 are, the same or different, -O-, -COO or -O-CO-, or a and b are, the same or different, 0 to 3, L 3 is -CO- or -CO-O-, R 3 is pyrrolidin-2-yl, pyrrolidin-3-yl, piperidin-2-yl, piperidin-3-yl, piperidin-4-yl, morpholin-2-yl, morpholin-3-yl, or alkyl having 1 to 6 carbon atoms or alkenyl having 3 to 6 carbon atoms substituted with 1 to 3 substituent(s), which is(are), the same or different, amino, monoalkylamino, dialkylamino, trialkylammonio, hydroxy, alkoxy, carbamoyl, monoalkylcarbamoyl, dialkylcarbamoyl, pyrrolidinyl, piperidyl or morpholinyl, wherein at least one of the substituents is amino, monoalkylamino, dialkylamino, trialkylammonio, pyrrolidinyl, piperidyl or morpholinyl, and L 1 and L 2 are, the same or different, -O-, -CO-O- or -O-CO-.