The solid-phase synthesis of oligopeptide was achieved for the first time in a microfluidic device. We fabricated a microchannel (width 300 mum, depth 160 mum) with a bead trap on a glass plate. Resin beads were loaded in the bead trap for the solid-phase peptide synthesis, and the synthesis of pentapeptide (Met-enkephalin) was conducted in the microchannel. The yield of the synthesized pentapeptide was confirmed to be 20% by MALDI-TOF MS and HPLC analyses.