An ice maker includes an ice tray configured to receive water, where the ice tray includes a plurality of partition ribs that partition an inner space of the ice tray into a plurality of cells, an ejector that is configured to rotate relative to the ice tray, that is configured to cause rotation of ice pieces in a rotation direction relative to the ice tray, and that is configured to discharge the ice pieces from the ice tray, and a motor configured to drive the ejector to rotate in a first direction and a second direction opposite to the first direction. The ice tray further includes a protrusion portion that is located at each cell, that protrudes from a lower surface of each cell, and that extends along the lower surface of each cell in a direction corresponding to the rotation direction of the ice pieces relative to the ice tray.