A novel use is disclosed of liposomes that contain phytosterol (e.g., ²-sitosterol, campesterol, stigmasterol, brassicasterol, ergosterol, and ergostadienol, and so forth). It has been newly discovered that liposomes that contain phytosterol have a cancer metastasis inhibiting activity. Cancer metastasis is inhibited by the oral administration of liposomes that contain phytosterol and these liposomes are therefore useful for the prevention and treatment of cancer.