A methanol steam microreactor with a replaceable catalytically coated plate structure was designed. A splitting-jointing flow (SJF) design was proposed to increase the efficiency. Stainless-steel plates were coated with a Cu/Zn/Fe nanocatalyst. Electrophoretic deposition served as a uniform and controllable coating technique to evaluate the performance of the nanocatalyst and the microchannel design. The functioning of the SJF design for methanol conversion was found to be only slightly dependent on the plate length. The yield of H-2 varied with different lengths in the SJF, while the direct parallel microchannel showed a lower performance by reducing the plate length. Comparing a quartz packed-bed reactor with a microreactor proved the strong dependency of methanol conversion on the accessibility of the reactants to the nanocatalyst sites.