The invention relates to a method for detecting an abnormality of a temperature sensor. A plurality of temperature sensors are preliminarily grouped for each of predetermined attachment areas of a machine tool, and after a temperature of each part is measured in S1, the detected temperatures are classified in S2 for each of the grouped attachment areas, and then sorted in descending order in S3. Subsequently, a difference ΔT between any closest two of the detected temperatures is obtained in S4, and then compared with a preset limit value γ in S5, when ΔT exceeds the limit value γ, temperature sensors in a corresponding attachment area are determined abnormal in S6, and an alarm is displayed.