The present invention provides a cationic lipid which can be used for a delivery of a nucleic acid into the cytoplasm of a cell. The cationic lipid of the present invention is, for an example, a compound or a pharmaceutically acceptable salt thereof represented by the following formula (1).本發明提供可用於向細胞質傳遞核酸之陽離子性脂質。本發明之陽離子性脂質例如為下述式(1)所表示之化合物或其藥劑學上所容許的鹽。