To supply H, for a small proton exchange membrane fuel cell (PEMFC) as a power source for portable electronic devices, a multi-layered microreactor system with a methanol reformer was developed. The microreactor consists of four units (a methanol reformer with a catalytic combustor, a CO remover, and two vaporizers) and was designed using thermal simulations to establish an appropriate temperature distribution for each reaction. The microreactor was constructed from thirteen microchanneled glass plates stacked with anodic bonding and placed in a vacuum package for thermal isolation. An appropriate catalyst for each reaction was deposited on the microchannel of each reactor. When the microreactor was heated by applying voltage to a thin film heater attached to one side of the reformer, the temperature distribution observed for each unit approximated the simulated results. Finally, methanol reforming was achieved in the microreactor using heat supplied from the internal catalytic combustor. The reforming temperature of the microreactor could be maintained at 280 degrees C without a supply of electrical power. A hydrogen production rate sufficient to generate 2.5 W of electrical power was obtained.