This paper describes a novel method for estimating the thermal conductivity of soft materials and liquids using a thermophysical handy tester. A thermophysical handy tester utilizing a point-contact method is a fast, non-invasive and in-situ device for measuring the thermophysical properties of a material. This device has been applied to various industrial materials for deterioration diagnosis and quality inspection. However, it cannot be applied to soft or liquid materials precisely. In this study, an inverse analysis of this device was conducted to make it applicable to the measurement of the thermophysical properties of these materials. In the proposed inverse analysis, a real coded genetic algorithm (GA) was used to minimize the objective function. First, a calibration experiment of the device was conducted by using agar-gelled water (0.5 wt%) to determine the apparatus constant. Then, this method was validated by measuring the thermal conductivity of some materials such as glycerol and ethanol. It was found that, the estimated thermal conductivities show good agreement with the reference values. Moreover, estimations of thermal conductivities of various materials including biological materials such as fat and muscle of pig were carried out, and reasonable values could be obtained by a proposed method in this study. However, it was revealed that there were the upper and lower limit in the measurable range which is 0.14 - 1.3 W/(m·K). Thus, a proposed method has a possibility to be effective for the measurement of thermal conductivity of the biological tissue, because the range of that is generally 0.2 - 0.6 W/(m·K).