Growth behavior of a single sodium chloride seed crystal mounted on the bottom of a flow cell was observed by an optical microscope. When a small crystal (a few to 50 mu m), suspended in the solution, attached by chance to the surface of the seed crystal, macro-steps appeared on the crystal surface in succession. These macro-steps were combined to a large macro-step,which was left behind by the following macro-steps. At this moment of over-passing, liquid inclusion(s) was formed. This formation was observed not only on the surface where a small crystal adhered but also on any other crystal surface. The macro-steps are assumed to be formed by bunching of molecular size steps, which are generated from a dislocation caused by mechanical stress induced by adhesion of a small crystal. The instantaneous (up to several tens of minutes) growth enhancement is also observed. This enhancement is attributed to the number increase of molecular size steps. This type of liquid inclusion formation influencing lowering of crystal purity is pointed out to he important from an industrial point of view.