A package for the power source of mobile electronic devices based on micro solid oxide fuel cells (micro-SOFCs) was designed considering thermal management. The package should suppress its surface temperature lower than harmless value for other electrical circuits, and thermal consistency should be kept. In addition, other functions such as gas flow and electrical connection were installed into the package. Hence, high performance thermal insulation structure with good machinability was necessary. We applied thermal insulation structure made of Si wafers and glasses by MEMS technologies. The convection heat transfer was prevented by the structure equipped with a vacuum zone. Experimental and theoretical consideration revealed that the purpose could be achieved at apparent thermal conductivity of the structure lower than 0.02 W/ mK. In accordance with the consideration, a package was designed, and its thermal insulation performances were evaluated.