The authors have been studying a technique for separating hydrogen from a gas mixture utilizing a thermal diffusion phenomenon called the Soret effect. The Soret effect is a separation phenomenon driven by temperature differences, and the authors aim to extract hydrogen from gas mixtures utilizing the phenomenon. The authors succeeded in reproducing the trend of hydrogen separation experiments using numerical thermo-fluid analysis, and predicted the separation performance with high accuracy. In the present paper, the results of a device structure that can provide a more effective temperature difference are reported with thermo-fluid analysis, which show a significant separation improvement.