Abstract: A method for measuring the temperature of rotating machining tools, comprising providing an optical fiber sensor; inserting said optical fiber sensor into the rotating machining tool; directing light from a light source into said optical fiber of said fiber sensor; detecting changes of optical properties of said optical fiber sensor as a function of temperature in the reflected light leaving said optical fiber; and correlating said changes of optical properties to the temperature of the machining tool. The apparatus comprises the respective elements. The present invention proposes a solution for the temperature measurement in rotating machining tools which avoids the transmission of electrical signals, and which can be integrated even in very small machining tools such as small dental drills. It continuously measures the temperature of the machining tool and is not sensitive to liquid coolants.