Effective thermal conductivity of LaNi5 powder packed bed was analyzed with a miniaturized guarded hot-plate (GHP) apparatus. Here, GHP was designed for precise measurement of effective thermal conductivity of metal-hydride powders even with small sample amounts (2.12 x 10(4) mm(3)). Dimensions of sample container and apparatus were determined through two-dimensional (2-D) steady-state heat conduction analysis. Calibration experiment and uncertainty analysis were conducted to validate the accuracy of the GHP. Based on the measurements of the residual thermal conductivity of the LaNi5 packed bed, effect of particle size on contact factor of LaNi5 packed bed was estimated. By applying the Yagi and Kunii (YK) model to the effective thermal conductivity of LaNi5 packed bed, effect of contact factor and gas thermal conductivity on characteristic length of gas film were newly analyzed. Factors of YK model were modified in present work and validated through comparison with experimental data from previous literature.