Thermal conductivity is a quantity which governs the heat transfer in a material. After increasing importance of efficiency in power generation systems and cooling mechanisms in micro-structures, many measurement methods have been developed to explore the thermal conductivity in micro and nano-sized materials. However, complexity in experimental setups, difficulties in the fabrication of devices required for measurements, and lacking exact solutions to thermal equations limit the usability of the methods to a class of materials. It is particularly challenging to study atomically thin metallic materials. To tackle this challenge, we have developed a new thermal conductivity measurement method based on the temperature dependent electrical resistance change and analyzed our method analytically and numerically by finite element method. We applied our method to 2H-TaS2 and found thermal conductivity as 9.55 1.27 W/m.K. Thermal conductivity value of TaS2, a metallic transition metal dichalcogenide was measured for the first time. This is supported by Wiedemann-Franz law and thermal conductivity of similar materials such as 2H-TaSe2 and 1T-TaS2. The method can be applied to semiconducting thin materials as well and is superior to other methods in various ways.