A new fully automated apparatus for measuring the thermal conductivity of liquids is described. This apparatus has been developed to meet the needs of industrial applications. The principle of the measurement is based on the absolute transient hot‐wire method. All data acquisition and instrument control can be performed using a microcomputer. After filling with a sample liquid in a cell the apparatus can automatically measure the thermal conductivity at the desired temperature without any manual procedures. The automated procedures include an algorithm to determine onset time of natural convection. The applicability of the apparatus has been tested to measure the thermal conductivity of toluene at room temperature and the results have an estimated accuracy of ±1.0 to ±1.5% depending on a sample to be measured.