A focused ion beam (FIB) technique was applied to the preparation of a cross-sectional transmission electron microscopy (TEM) specimen of Zn-coated steels. Two types of steel were observed. One is an as-dipped steel (galvanized (GI) steel) and the other is a steel annealed for 20 s at 773 K after dipping in a molten zinc bath (gal vannealed (GA) steel). For both steels, the whole depth of the Zn coating from the outermost surface to the steel substrate was observed and the microstructures characterized.