An immunostimulatory lipoplex is provided. The immunostimulatory lipoplex includes a liposome and at least one immunostimulatory nucleic acid drug, and the immunostimulatory nucleic acid drug is complexed with the liposome The liposome includes 40 to 85 mol % of cationic lipid, 10 to 50 mol % of cholesterol, and 0.001 to 20 mol % of modified polyethylene glycol lipid. A pharmaceutical composition including the immunostimulatory lipoplex is also provided