The present invention provides a lipid nano-particles, which allow nucleic acids to be easily introduced into cells, comprising a cationic lipid represented by formula (I)(wherein: R1 and R2 are, the same or different, alkenyl, etc, andX3 is absent or is alkyl, etc,X1 and X2 are hydrogen atoms, or are combined together to form a single bond or alkylene, andY1 is absent or anion,L1 is a single bond, etc,R3 is alkyl, etc), and the like.