An image forming apparatus includes a heating member, a temperature sensor to output detection values for determining a temperature of the heating member, a first amplifier to amplify a difference value between the detection values with a first amplification factor, a second amplifier to amplify the difference value with a second amplification factor, a converter to generate first temperature information through analog-to-digital conversion of the difference value amplified by the first amplifier, generate second temperature information through analog-to-digital conversion of the difference value amplified by the second amplifier, and generate compensation temperature information, and a temperature determiner to determine the temperature of the heating member based on the second temperature information and the compensation temperature information, in a particular temperature range, and determine the temperature of the heating member based on the first temperature information and the compensation temperature information, outside the particular temperature range.