We report a hydrodynamic instability related to the periodic growth of needlelike crystals observed in thin aqueous-solution films of Ba (N03)2 with the free surface in isothermal conditions. The oscilla-tion of the aqueous-solution film. in which the solution film separates and recontacts with the needle-like crystal periodically, has been investigated using in situ observations with interference-contrast mi-croscopy. Our experiments indicate that this phenomenon derives from the interplay of the Marangoni effect and the wetting effect.