The graphoepitaxy of KCl was investigated through depositing the KCl film on a Si substrate having square‐wave grating by means of vacuum evaporation, and then exposing the film to water vapor. The deposited crystallites grew to become rectangular parallelepipeds 3–4 &mgr;m in diameter because of the water adsorbed on the surface. During the growth, crystallite orientation was aligned along the grating by the effect of the groove walls. A well‐aligned in‐plane orientation was obtained when the groove width of the grating was kept smaller than the width of the grown crystallite and when the groove depth was close to the crystallite’s height.