An object accommodated in an internal space of a freezer is quickly cooled to a predetermined temperature with preventing water from freezing while an oscillating electric field of, preferably, a variable frequency in the range of 50 Hz to 5 MHz and/or a magnetic field are applied to the object, or further ionic air is added to clod air, and subsequently the object is instantaneously frozen at the predetermined temperature. Preferably, the magnetic field is a static magnetic field and/or a variable magnetic field.