PURPOSE: To prevent the environment degradation of working place by arranging a shaft cover fixed its position at the boundary zone between the molten solder in solder bath and the air layer on its surface around a shaft.

CONSTITUTION: A wave soldering device is provided with a solder bath 1 and solder wave device 2. The solder wave device 2 is composed of a chamber 3 accommodated in a solder bath 1, a propeller 4 in the chamber, a shaft of which one end is connected to the propeller and the other end is extended outside the solder bath 1 and a motor 6 to drive the shaft. Around the shaft 5, a shaft cover 10, which fixes its position at the boundary zone between the molten solder accommodated in the solder bath 1 and air layer covering its surface, is arranged. By this method, at rotating the shaft 5, the surface of molten solder around the shaft does not have wave, accordingly, oxide film is hardly destroyed, reducing the generation of solder oxide.