This study investigates the influence of cutting fluid on the cutting temperature in end milling of a titanium alloy. As the cutting temperature, the tool edge temperature was measured using a two-color pyrometer with an optical fiber. A helical cutter with an indexable insert of 50-mm diameter was used. The cutting speed was set at 100 m/min. The feed rate was set at 0.1 mm/tooth. The radial and the axial depth of cut were set at 12 and 5 mm, respectively. Under this cutting condition, a method for measuring the transitional tool edge temperature in one cut was established. One cut took ～15.22 ms under this cutting condition. In the case of up cut, the temperature under dry conditions increased rapidly at the start of cutting and then converged. The temperature under wet conditions increased slowly until 7 ms and then converged. In the case of down cut, the temperature under dry conditions increased rapidly at the start of one cut and then remained almost constant, before increasing slightly at the end of one cut. The temperature under wet condition increased rapidly at the start of one cut and then decreased slowly until the end of one cut. The larger tool edge temperature reduction effect caused by the cutting fluid was obtained near the end of one cut, where the uncut chip thickness was smaller. Due to the small uncut chip thickness, the cutting fluid is effective at the end of each contact between tool and workpiece and then the cutting edge temperature decreases considerably.