Wettability of Cu and Cu-Sn intermetallic compound was investigated in terms of its surface oxidation. Cu₂O layer of about 55nm thick was formed on the surface of Cu during the heat treatment at 150 C for 2h in the air, which had a little influence on its wettability. On the other hand, the surface oxidation of Cu-Sn intermetallic compound caused an appreciable reduction in its wettability. The surface of the oxidized Cu-Sn intermetallic compound was covered with an amorphous layer of about 5nm thick. The galvanostatic coulometry analysis suggested that the amorphous layer was a Cu-Sn complex oxide, which was more difficult to reduce owing to its cathodic potential lower than Cu₂O or SnO.