A thermometer calibration method and fixed-point temperature realizing apparatus uses a fixed-point cell including a crucible of carbon and a fixed-point material enclosed in the crucible. The fixed-point material is a eutectic structure of carbide and carbon. The fixed-point cell is placed in a furnace for increasing and decreasing the environmental temperature of the cell. A thermometer to be calibrated is used to measure temperature variations in the cell and calibrated based on the temperature variations thus measured.