A life estimating method for a heater wire utilizes data obtained during a period (e.g., a temperature rising period), in which a sign of disconnection of the heater wire is likely to be seen. This method includes detecting a maximum magnitude value of electric power supplied to the heater wire during the temperature rising period for elevating the temperature to a heating temperature prior to providing a heating process to a wafer or wafers. The method further includes obtaining an index indicative of a magnitude of the amplitude of the electric power, and giving notice that the heater wire is approaching the end of its life when the indexes respectively indicate that the electric power magnitude and the amplitude magnitude exceed threshold values respectively.