The present invention provides a cationic lipid which is able to be used for nucleic acid delivery to the cytoplasm. A cationic lipid according to the present invention is, for example, a compound represented by formula (1a) or a pharmaceutically acceptable salt thereof. (In formula (1a), each of L1 and L2 independently represent an alkylene group having 3-10 carbon atoms； each of R1 and R2 independently represent an alkyl group having 4-22 carbon atoms or an alkenyl group having 4-22 carbon atoms； X1 represents a single bond or —；CO—；O—；； and ring P represents one of formulae (P-1) to (P-5).) (In formulae (P-1) to (P-5), R3 represents an alkyl group having 1-3 carbon atoms.)
