PURPOSE: To enhance response with respect to the change in the heater power of a vacuum vapor deposition furnace, in continuously applying Zn on a steel strip by vacuum vapor deposition, by using a fibrous heat insulating material as the material for the furnace wall of the vacuum vapor deposition furnace to reduce the heat capacity of the heat insulating material to a large extent.

CONSTITUTION: A steel strip 1 is continuously passed through a vacuum container 2 and a molten metal plating material 5 such as Zn or Al in an evaporation pot 3 is evaporated and injected from an evaporation port to vapor deposit a plating layer comprising Zn or Al on the surface of the steel strip 1. In this case, by using a fibrous heat insulating material 7 used in the inner surface of the evaporation pot 3, the heat capacity thereof is reduced to a large extent as compared to conventional refractory brick and, because said fibrous heat insulating material is fast in response with respect to the change in the heater power of the heater 4 of the evaporation pot 3 and has good deformability, it can be provided to the evaporation pot 3 in low cost.