Ice maker including an ice making container (100) having a plurality of cavities (120) for forming ice, a heater body (210) on one side of the ice making container for selective generation of heat, and heating bars (220) each extended from the heater body to the cavity by a predetermined length with a profile in conformity with a bottom surface profile of the cavity (120) with a gap to the bottom surface such that the heating bar (220) is submerged under water in the cavity for causing a temperature gradient during ice making.