A malfunction diagnosis apparatus includes: a first temperature detector; a second temperature detector that is placed in a different location from where the first temperature detector is placed; a difference value calculation device calculates a difference value between a detection value from the first temperature detector and a detection value from the second temperature detector; a mapping device carries out mapping of the difference value and calculates a correction value using the frequency of the difference value; a malfunction diagnosis device diagnoses whether or not there is a malfunction in the first temperature detector and the second temperature detector; and a recovery device calculates, as a detection value of the first or second temperature detector judged to be malfunctioning, a value by adding the correction value to a detection value from the first or second temperature detector judged not to be malfunctioning.