An automatic ice maker for use in freezing compartments of the refrigerators. A planar stop arm is used as an ice cube detecting device for detecting a sufficient ice cubes stored in a bin arranged below a tray for making ice cubes. The stop arm can be swung between the bin for storing therein the ice cubes and the tray in order prevent the ice cubes stored in the bin from being molten by a head radiation from a heater provided on the tray.