An experimental study was performed on the effective thermal conductivity of screen wicks saturated with a liquid. A planar heat pipe was employed to determine the effective thermal conductivity, and its value was calculated from the heat transfer coefficient in the condenser of the heat pipe positioned horizontally. A comparison of the existing correlations with the present experimental data indicated that the effective thermal conductivity of screen wicks could be predicted by Maxwell's equation derived for the case where wick materials (or screens) were dispersed in working liquids. It was also found that, in predicting the effective thermal conductivity by Maxwell's equation, the thickness and porosity of multilayer screen wicks had to be estimated accurately by taking account of the intermeshing between screen layers.