Disclosed is an automatic ice maker which surely removes ice cubes from an ice-making unit and improves an ice-making efficiency. When the automatic ice maker starts a deicing operation, a hot gas is supplied to an evaporator and deicing water is supplied to the ice-making unit from a deicing water sprinkler to turn the frozen state at the frozen surfaces between the ice-making unit and ice cubes to a liquefaction state. When the deicing operation makes some progression and a temperature detecting unit detects that the temperature of the evaporator has reached a set temperature, a circulation pump is driven after elapse of the first set temperature to supply ice-making water to the ice-making unit from an ice-making sprinkler, promoting further separation of the ice cubes.