A new method for measuring thermal conductivities of gases and liquids was established by demonstrating the measurement of five kinds of liquid and air. It uses a sensor named "micro-beam sensor" that is a similar to 10-mu m-long free-standing platinum membrane suspended across a trench on a silicon substrate and heated in a sample by DC. This method is unique in that it is a steady-state measurement but free from the effect of natural convection owing to the micrometer size of the sensor. Improving the method for precisely determining the temperature of the sensor and modifying the device from those used in our previous feasibility study, we successfully measured the thermal conductivity ranging from similar to 0.03 to similar to 0.6 W/(m.K) within 4% error. (C) 2017 Elsevier Ltd. All rights reserved.