The effect of minimum quantity lubrication (MQL) method in end milling of stainless steel and titanium alloy that are typical difficult-to-cut materials with coated carbide tool is investigated. The effect is mainly evaluated by tool flank temperature, cutting force and tool wear behavior. The tool flank temperature is measured using a two-color pyrometer with an optical fiber having small measurement area and high response speed under non-contact condition with tool. In MQL cutting of SUS304 and Ti-6Al-4V at cutting speed v=25m/min, the tool flank temperature decreases approximately 50°C and 100°C than the case of dry cutting respectively, and the effect of MQL on tool flank temperature is especially obtained in low-speed cutting. On the other hand, the tool flank temperature in MQL cutting of Ti-6Al-4V is higher than the case of dry cutting in cutting speed v=100m/min or more. In the high-speed cutting of Ti-6Al-4V, it is observed that the several chips adhere on the rake face of cutting edge. In addition, the output voltages from detector are obtained when the adhesion chips on the cutting edge pass through the measurement area of two-color pyrometer. In the case of the SUS304, the feed and thrust force are decreased by the supplying oil mist in high speed cutting. The generation of micro-crack at cutting edge is contained by applying MQL even high speed cutting of Ti-6Al-4V that is not obtained the effect of temperature decreasing.