The corrosion resistance of soft magnetic films is an important property to be considered in the manufacture of magnetic devices. We investigated the corrosion behavior of the electrodeposited CoNiFe him with desired soft magnetic properties by varying the crystalline structure and the amount of included sulfur. The corrosion property in 2.5% NaCl solution depends largely on the sulfur content and also on the structure of the film. Although the CoNiFe film contains more than 13 atom % Fe, the film of face-centered to body-centered cubic mixed crystals exhibits a high anticorrosion property because of very small grain size with essentially no sulfur inclusion (<0.1 atom %).