Abstract: With a method of storing meat stored in a refrigerator or a freezer after a lump of meat is prepared into small portions, which includes irradiating the meat with positive ions and negative ions before storage in the refrigerator or the freezer, a method of extending a durable life of food requiring storage by refrigeration, a method of suppressing growth of fungi developed at a surface of food requiring storage by refrigeration, and an ion irradiation apparatus which can suitably be used for these methods, a method allowing suppression of growth of fungi adhering to food (in particular, meat) requiring storage by refrigeration, a method of thereby extending a durable life of food requiring storage by refrigeration, and an apparatus which can suitably be used for these methods are provided.