An ice maker comprises: a first tray forming a part of an ice-making cell; a second tray forming another part of the ice-making cell; and a heater which is disposed so as to be adjacent to the first or the second tray, wherein the heater operates during a period when cold air is supplied to the first tray and the second tray and ice making takes place, and supplies heat to the first tray and/or the second tray.