In this study, emissivities of metals-steels, titanium alloy and aluminum-have been measured and analized for the better utilization of radiation thermometry. In the experimentation, true temperatures were determined by thermocouple to compare with the luminance temperatures which were measured by two types of radiation thermometer, one is for high temperature range (600°C∼1600°C) using Si-photo diode as a thermal sensor and the other is for medium range (250°C∼850°C) by Ge-photo diode.Results of this investigation are summarized as follows.(1) In the case of steels, the emissivity can be fixed to 0.8 regardless of kind of steel.(2) In the case of titanium alloys, the setting must be adjusted from 0.6 to 0.83 according to the alloy content, especially to content of vanadium, to reduce the measuring error.(3) Emissivity of aluminum is very small, which has a value of about 0.2, so it is important to set the value correctly for accurate measurement.