PURPOSE: To prevent the intrusion of Zn vapor into the snout to be immersed into a plating bath at the time of hot dip coating of a steel strip with a Zn-Al alloy, the adhesion thereof on a steel strip and the generation of a plating defect by forming the outlet side end of the snout to a specific structure.

CONSTITUTION: The outlet side end of the snout 31 for introducing the steel strip W into the hot dip coating bath at the time of hot dip coating of the steel strip with the Zn-Al alloy by using a galvanizing device is made into a narrow cross section structure having a guide groove of a spherical weight to be used at the time of threading. The position of the steel strip W in a down chute 21 is detected by a position sensor 51 disposed in the upper part of the snout 31 at the time of plating and is inputted to a controller 54. This controller compares and computes this position with a preset adequate value and emits a signal to an actuator 53 to retreat this actuator and to oscillate the snout 31 together with the down chute 21, thereby normalizing the position in the snout to be generated from the plating bath. The adhesion of the solidified Zn in the snout on the steel strip W and the generation of the defective surface condition of the steel strip W and the plating defect are thus prevented.