We propose a method that allows us to evaluate the thermal conductivity of a conductive material that has thickness on the order of microns. The key feature of the proposed method is use of a complete thermoelectric device with electrodes and a substrate, while conventional methods measure the temperature gradient of thermoelectric materials directly without electrodes. The measured thermal conductivity of a ZnSb film annealed at 380°C in N₂ ambient for 16 min to 26 min is 1.2 W/m K to 1.4 W/m K. The measurement shows that thermoelectric film prepared by a screen-printing technique has lower thermal conductivity than bulk material (2.2 W/m K to 2.4 W/m K) because the screen-printing technique generates high porosity in the film. The lower measured thermal conductivity of the porous films compared with bulk material supports the reliability of the proposed measurement method.