The present invention provides a technique of introducing active ingredient, especially nucleic acids, into cells and cationic lipids used therein and the like.The solution means of the present inventions is the compounds represented by the following formula (I), or salts thereof. In formula, n represents an integer of 2 to 5, R represents a straight C1-5 alkyl, a straight C7-11 alkenyl or a straight C11 alkadienyl, the wave lines each independently represents the binding of cis-form or trans-form.
