Provided are: a galvannealed steel sheet, improved in the adhesiveness of a plated layer with a base steel sheet, as a galvannealed steel sheet, prepared by using a high-strength steel sheet as a base material; and a method for producing the galvannealed steel sheet. A galvannealed layer is formed on the base steel sheet including a high-strength steel having a predetermined composition. The average amount of Fe in the galvannealed layer is 8.0 to 12.0%. The absolute value of a difference (Fe) between the amount of Fe in the vicinity of an interface with the base steel sheet and the amount of Fe in the vicinity of the external surface of the plated layer in the plated layer is 0.0 to 3.0%.

A metallic material with a first microstructure is coated in a bath with a coating to form a coated metallic material. The coating has a liquidus temperature and the bath has an operating temperature that is higher than the liquidus temperature. The first microstructure of the metallic material is altered by the application of the coating to an alternative microstructure. The coating includes a dopant which acts as a temperature reducing agent.