An icemaker comprising: a rotatable ice tray having at least one column of ice making chambers formed therein to make ice and a rotating shaft; an ejector rotatably provided in the ice making chamber to eject the ice formed in the ice making chamber; an operation device having a motor connected to the rotating shaft of the ice tray so as to rotate the ice tray; and a separation device which separates the ice from the ice tray, wherein the separation device is a heater which heats the ice tray, wherein the ejector comprises: a shaft rotatably mounted at the ice tray in a longitudinal direction of the ice tray, both opposite ends of the shaft being hingedly connected to the upper portion of the ice making chamber; an ejector fin projected each predetermined distance on the shaft so that the ejector fin is positioned in each ice making chamber to eject the ice of the ice tray as the shaft rotates; and an inertial operation part which generates rotational force due to its weight when the ice tray rotates, to rotate the shaft relatively with respect to the ice tray, the inertial operation part having a weight and an arm having an end connected to an end of the shaft and the other end connected to the weight wherein the arm positions the weight spaced apart a predetermined distance from a center of the shaft. a rotatable ice tray having at least one column of ice making chambers formed therein to make ice and a rotating shaft; an ejector rotatably provided in the ice making chamber to eject the ice formed in the ice making chamber; an operation device having a motor connected to the rotating shaft of the ice tray so as to rotate the ice tray; and a separation device which separates the ice from the ice tray, wherein the separation device is a heater which heats the ice tray, wherein the ejector comprises: a shaft rotatably mounted at the ice tray in a longitudinal direction of the ice tray, both opposite ends of the shaft being hingedly connected to the upper portion of the ice making chamber; an ejector fin projected each predetermined distance on the shaft so that the ejector fin is positioned in each ice making chamber to eject the ice of the ice tray as the shaft rotates; and an inertial operation part which generates rotational force due to its weight when the ice tray rotates, to rotate the shaft relatively with respect to the ice tray, the inertial operation part having a weight and an arm having an end connected to an end of the shaft and the other end connected to the weight wherein the arm positions the weight spaced apart a predetermined distance from a center of the shaft. a shaft rotatably mounted at the ice tray in a longitudinal direction of the ice tray, both opposite ends of the shaft being hingedly connected to the upper portion of the ice making chamber; an ejector fin projected each predetermined distance on the shaft so that the ejector fin is positioned in each ice making chamber to eject the ice of the ice tray as the shaft rotates; and an inertial operation part which generates rotational force due to its weight when the ice tray rotates, to rotate the shaft relatively with respect to the ice tray, the inertial operation part having a weight and an arm having an end connected to an end of the shaft and the other end connected to the weight wherein the arm positions the weight spaced apart a predetermined distance from a center of the shaft.