PURPOSE: To prevent the occurrence of surface defects by spraying a gas upon a substance to be hot dipped to remove foreign matter immediately before the substance enters a molten metal.

CONSTITUTION: Foreign matter removing device 4, 4a are attached to a naked portion of snout 1 over the surface of molten metal 2. Devices 4, 4a are composed of two gas feed pipes 5, 5a inserted into snout 1 so that they are positioned at both sides of substance 3 to be hot dipped, valves 6, 6a attached to pipes 5, 5a outside snout 1, respectively, pressure gauges 7, 7a attached to each pipe 5, 5a before and behind each valve 6, 6a, and a plurality of nozzles 8, 8a attached to pipes 5, 5a in line, respectively. When valves 6, 6a are opened to feed an inert gas or the like, the gas is radiately spouted from nozzles 8, 8a against the boundary where substance 3 enters molten metal 2 to remove foreign matter stuck to substance 3.