Provided is a method of controlling temperatures of objects to be heated in a heating unit by adjusting a heating rate of each of a plurality of heating elements, based on temperature detection values detected at a plurality of temperature detection elements, wherein the plurality of temperature detection elements are positioned at different positions and the plurality of heating elements are positioned at different positions. The method includes estimating a temperature of each of the plurality of temperature detection elements by using a first estimation algorithm when one of the plurality of temperature detection elements is broken, based on the temperature detection values of the temperature detection elements excluding the broken temperature detection element, and controlling the temperatures of the objects to be heated based on the estimated temperatures.