To produce a hot-dip coated steel strip, in which the coated amount is controlled at high accuracy.

A camera 4 for observing the steel strip S drawn up from a hot dipping bath, from the width direction, is arranged at a position apart from the steel strip S on the extending line in the width direction of the steel strip. A bonarization treatment is applied to a picture picked up with the camera 4 and a displacing amount from the reference position of the steel strip S is calculated and a wiping nozzle 3 is controlled to shift in the normal line direction on the surface of the steel strip so that the distance from the wiping nozzle 3 faced to both surfaces of the steel strip S to the both surfaces of the steel strip becomes constant, based on the calculated value.