A malfunction diagnosis apparatus comprising: a first temperature detection circuit that is placed inside diagnosis-target equipment; a second temperature detection circuit that is placed in a different location inside the diagnosis-target equipment from where the first temperature detection circuit is placed; a difference value calculation device that is arranged to calculate a difference value between a detection value from the first temperature detection circuit and a detection value from the second temperature detection circuit; a malfunction diagnosis device that is arranged to diagnose whether or not there is a malfunction in the first temperature detection circuit and the second temperature detection circuit, characterized by: a mapping device that is arranged to carry out mapping of a plurality of difference values calculated by said difference value calculation device and to calculate a correction value using the frequency of occurrence of the difference values; and a recovery device that is arranged to calculate, as a detection value of the first or second temperature detection circuit judged to be malfunctioning, a value by adding the correction value to a detection value from the first or second temperature detection circuit judged not to be malfunctioning, and transmit the calculated value to the diagnosis-target equipment. a first temperature detection circuit that is placed inside diagnosis-target equipment; a second temperature detection circuit that is placed in a different location inside the diagnosis-target equipment from where the first temperature detection circuit is placed; a difference value calculation device that is arranged to calculate a difference value between a detection value from the first temperature detection circuit and a detection value from the second temperature detection circuit; a malfunction diagnosis device that is arranged to diagnose whether or not there is a malfunction in the first temperature detection circuit and the second temperature detection circuit, characterized by: a mapping device that is arranged to carry out mapping of a plurality of difference values calculated by said difference value calculation device and to calculate a correction value using the frequency of occurrence of the difference values; and a recovery device that is arranged to calculate, as a detection value of the first or second temperature detection circuit judged to be malfunctioning, a value by adding the correction value to a detection value from the first or second temperature detection circuit judged not to be malfunctioning, and transmit the calculated value to the diagnosis-target equipment. a mapping device that is arranged to carry out mapping of a plurality of difference values calculated by said difference value calculation device and to calculate a correction value using the frequency of occurrence of the difference values; and a recovery device that is arranged to calculate, as a detection value of the first or second temperature detection circuit judged to be malfunctioning, a value by adding the correction value to a detection value from the first or second temperature detection circuit judged not to be malfunctioning, and transmit the calculated value to the diagnosis-target equipment.