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, and X3 is absent or is alkyl, etc, X1 and X2 are hydrogen atoms, or are combined together to form a single bond or alkylene, and Y1 is absent or anion, L1 is a single bond, etc, R3 is alkyl, etc), and a cationic lipid represented by formula (II) (wherein: R4 and R5 are, the same or different, alkenyl, etc, and X4 and X5 are hydrogen atoms, or are combined together to form a single bond or alkylene, and X6 is absent or is alkyl, etc, Y2 is absent or anion, a and b are, the same or different, 0 to 3, and L4 is a single bond, etc, R6 is alkyl, etc, L2 and L3 are -O-, -CO-O- or -O-CO-), and the like.本發明提供一種含有例如將核酸容易地導入至細胞內等之陽離子性脂質的藥物傳遞用脂質奈米粒子等,該脂質奈米粒子含有下述式(I)所表示之陽離子性脂質及下述式(II)所表示之陽離子性脂質。(式中,R1及R2為相同或不同,而為烯基等,X3不存在,或為烷基等,X1及X2為氫原子,或者一併形成單鍵或伸烷基,Y1不存在,或為陰離子,L1為單鍵等,R3為烷基等)(式中,R4及R5為相同或不同,而為烯基等,X4及X5為氫原子,或者一併形成單鍵或伸烷基,X6不存在,或為烷基等,Y2不存在,或為陰離子,a及b為相同或不同,而為0~3,L4為單鍵等,R6為烷基等,L2及L3為-O-、-CO-O-或-O-CO-)
