An ice maker that is controlled by a signal received from a refrigerator controller installed in a refrigerator, the ice maker comprising: a motor unit configured to generate a rotational force corresponding to the signal; a driving unit comprising a gear group rotated by the motor unit; and an ice tray configured to be twisted by an operation of the gear group, and is adapted to contain water therein to make ice, wherein the ice tray is configured to change a rotational speed one or more times in a rotation section where the ice tray is twisted by the rotational force corresponding to a rotational speed formed at the time of interlocking between gears in the gear group, characterised in that the gear group comprises: a plurality of gears to which the rotational force of the motor unit is transferred, and having a gear ratio to change the rotational speed and the rotational force; and an output unit engaged with one of the plurality of gears, and configured to transfer a speed-changed rotation to the outside of a control box, wherein the output unit comprises first and second output units configured to receive the rotational force of the motor unit through the plurality of gears, and formed as separate modules so as to be rotated at two gear ratios, wherein centers of rotation of the first and second output units have a same axis, the first and second output units have each gear teeth which are not formed in the 360 degree direction around the center of rotation of the output unit, but formed only at a predetermined section, wherein rotation sections in which the first and second output units are engaged with the respective gear are formed as different from each other, the first and second output units form pitch circles of different size, and the engagement of the first output unit and the engagement of the second output unit with the respective gears is sequentially performed, wherein the respective gears engaged with the first and second output units have a same axis of rotation and form pitch circles of different size. a motor unit configured to generate a rotational force corresponding to the signal; a driving unit comprising a gear group rotated by the motor unit; and an ice tray configured to be twisted by an operation of the gear group, and is adapted to contain water therein to make ice, wherein the ice tray is configured to change a rotational speed one or more times in a rotation section where the ice tray is twisted by the rotational force corresponding to a rotational speed formed at the time of interlocking between gears in the gear group, characterised in that the gear group comprises: a plurality of gears to which the rotational force of the motor unit is transferred, and having a gear ratio to change the rotational speed and the rotational force; and an output unit engaged with one of the plurality of gears, and configured to transfer a speed-changed rotation to the outside of a control box, wherein the output unit comprises first and second output units configured to receive the rotational force of the motor unit through the plurality of gears, and formed as separate modules so as to be rotated at two gear ratios, a plurality of gears to which the rotational force of the motor unit is transferred, and having a gear ratio to change the rotational speed and the rotational force; and an output unit engaged with one of the plurality of gears, and configured to transfer a speed-changed rotation to the outside of a control box, wherein the output unit comprises first and second output units configured to receive the rotational force of the motor unit through the plurality of gears, and formed as separate modules so as to be rotated at two gear ratios, wherein centers of rotation of the first and second output units have a same axis, the first and second output units have each gear teeth which are not formed in the 360 degree direction around the center of rotation of the output unit, but formed only at a predetermined section, wherein rotation sections in which the first and second output units are engaged with the respective gear are formed as different from each other, the first and second output units form pitch circles of different size, and the engagement of the first output unit and the engagement of the second output unit with the respective gears is sequentially performed, wherein the respective gears engaged with the first and second output units have a same axis of rotation and form pitch circles of different size.