A living cell is a huge network of chemical reactions in a compartmentalized microstructure. Realization of such a system using MEMS (microelectromechanical systems) technology would contribute to biological study and to development of an intelligent biochip. The authors have been focusing on protein synthesis in microreactors, because this process plays a central role in the chemical networks in living cells. This paper demonstrates that messenger RNA (mRNA)-polyuridylic acid-was translated into polypeptide-polyphenylalanine-in our primitive microreactor which was fabricated using conventional MEMS techniques: Silicon anisotropic etching and glass-silicon anodic bonding. The microreactor has a main reaction channel which is 14 millimeters long, 800 microns wide, and 20 microns deep. The amount of polyphenylalanine, which was synthesized in the channel, was determined using radioisotope assay.