A method was developed to measure tool temperature distribution within the tool by means of fine powders that have a constant melting point. The method involves observation of the boundary line formed by melted and unmelted powder scattered on the tool surface. It is clarified that temperature distribution within the tool is easily and accurately measured in this manner. Temperature distributions were compared with results obtained from analyses based on Loewen and Shaw’s theory, modified on the assumption that heat distribution due to friction along the rake face is not uniform but, rather, like real frictional distribution in cutting, and the fraction of heat flowing into the tool varies along the rake face.