The grinding temperature in the surface layer of a ceramic workpiece was measured using an IRP (infrared radiation pyrometer) connected by means of an optical fiber. Two types of optical fiber were employed: fluoride fiber and chalcogenide fiber. Si3N4, SiC, and Al2O3 were used as the work materials. The output waves of I.R.P. of Si3N4 and Al2O3 appear as curves with many peaks which are related to the infrared energy emitted from the cutting grains, but that of SiC shows no peaks at all. The highest grinding temperature was obtained in the case of Si3N4 whose grinding power is the largest of these three materials. The temperature distribution in the surface layer of the ceramics was much different from that of the steel.