1. A method for detecting abnormalities of a temperature sensor in a machine tool in which the plurality of temperature sensors are arranged at different positions, the method comprising the steps of: preliminarily grouping the temperature sensors into one or a plurality of predetermined attachment areas of the machine tool; respectively obtaining variations of detected temperatures by the plurality of temperature sensors belonging to the attachment areas; comparing each of the variations with a corresponding preset limit value; and determining the temperature sensors associated with variation to be abnormal when a variation exceeds the limit value.