An ice maker, comprising: a tray member comprising: an upper tray having an upper shell; and a lower tray having a lower shell; a driving unit disposed on a side of the tray member, the driving unit configured to linearly move, in a vertical direction, the lower tray to change between an attached position in which the upper shell is attached to the lower shell to define a spherical shell and a separated position in which the upper shell is separated from the lower shell, and to rotate the lower tray wherein the driving unit includes: a motor configured to provide rotation force; a pinion gear connected to a rotation shaft of the motor; and an ejecting unit that is disposed on a side of the tray member and that is configured to facilitate separation of an ice piece made in the spherical shell from at least one of the upper tray and the lower tray, characterized in that the driving unit further includes: a rack gear disposed on a side surface part of the tray member and engaged with the pinion gear on a first surface of the rack gear to move the lower tray, the rack gear including: a vertical part configured to vertically move the lower tray; and a rotation part that is curved with a predetermined curvature from an upper end of the vertical part and that is configured to rotate the lower tray; a guide roller contacting a second surface of the rack gear, the second surface of the rack gear being opposite to the first surface of the rack gear, wherein the ejecting unit includes: a lower heater mounted on an outer surface of the lower tray; an ejector (253,353), including: a connection member (253b,353b) horizontally extending; and an ejecting p in (253a,353a) vertically extending from the connection member (253b,353b) to pass through a top surface of the upper shell to separate the ice piece from the upper shell; and means for coupling the driving unit to the ejecting unit. a tray member comprising: an upper tray having an upper shell; and a lower tray having a lower shell; an upper tray having an upper shell; and a lower tray having a lower shell; a driving unit disposed on a side of the tray member, the driving unit configured to linearly move, in a vertical direction, the lower tray to change between an attached position in which the upper shell is attached to the lower shell to define a spherical shell and a separated position in which the upper shell is separated from the lower shell, and to rotate the lower tray wherein the driving unit includes: a motor configured to provide rotation force; a pinion gear connected to a rotation shaft of the motor; and an ejecting unit that is disposed on a side of the tray member and that is configured to facilitate separation of an ice piece made in the spherical shell from at least one of the upper tray and the lower tray, a motor configured to provide rotation force; a pinion gear connected to a rotation shaft of the motor; and an ejecting unit that is disposed on a side of the tray member and that is configured to facilitate separation of an ice piece made in the spherical shell from at least one of the upper tray and the lower tray, a rack gear disposed on a side surface part of the tray member and engaged with the pinion gear on a first surface of the rack gear to move the lower tray, the rack gear including: a vertical part configured to vertically move the lower tray; and a rotation part that is curved with a predetermined curvature from an upper end of the vertical part and that is configured to rotate the lower tray; a guide roller contacting a second surface of the rack gear, the second surface of the rack gear being opposite to the first surface of the rack gear, a vertical part configured to vertically move the lower tray; and a rotation part that is curved with a predetermined curvature from an upper end of the vertical part and that is configured to rotate the lower tray; a guide roller contacting a second surface of the rack gear, the second surface of the rack gear being opposite to the first surface of the rack gear, a lower heater mounted on an outer surface of the lower tray; an ejector (253,353), including: a connection member (253b,353b) horizontally extending; and an ejecting p in (253a,353a) vertically extending from the connection member (253b,353b) to pass through a top surface of the upper shell to separate the ice piece from the upper shell; and means for coupling the driving unit to the ejecting unit. a connection member (253b,353b) horizontally extending; and an ejecting p in (253a,353a) vertically extending from the connection member (253b,353b) to pass through a top surface of the upper shell to separate the ice piece from the upper shell; and means for coupling the driving unit to the ejecting unit.