Provided is an etchant composition for a silicon nitride film, and more particularly, to an etchant composition with a high selectivity to a silicon nitride film, which is used to etch away a silicon nitride film in semiconductor process and which selectively has a high etching rate for the silicon nitride film compared to a silicon oxide film in a high temperature etch process, in which the etchant composition with the high selectivity selectively etches the silicon nitride film at a selectivity of 2000:1 or higher between the silicon nitride film and the silicon oxide film which are in a stack structure, and minimizes damages to the silicon oxide film and etching rate, and does not cause re-growth of the silicon oxide film over the process time.