For thermal analyzing on the grinding phenomenon, it is necessary to measure the temperature of microscopic area in very short time. There are two representative methods, one is the thermocouple method and another one is the infrared radiation thermometer. The new type of infrared radiation thermometer with optical fiber was developed in the response time and the measurable area. The minimum response time was 3×10^<-6>s and the diameter of measurable area was limited to just 110×10^<-6>m. Consequently, this thermometer measured the exact grinding temperature that correlated with calibration curves of S45C, grinding wheel (WA80) and compared with the results of thermocouple(alumel-S45C). The obtained temperature depended on the heat flow rate during the grinding operation and the oxidation of removed chips. The measured signal also indicated two parts, one was the base part and another was the impulse part. The heat energy generated by the oxidation was larger than the total amount of the energy supplied by the grinding operation.