Some factors taking part in the landslide observed in three areas have been re-searched. It has resulted in that scrutiny for microgeologic environs as well as for average permeability or any other mechanical properties represented by the superficial deposits including the clayey matters is much more significant than that for general geology composing the related region, though not to be neglected because of emergence of the landslides in considerably restricted zones, for the grain-size proportion in the deposits, and for the species of clay minerals in relation to difference in their characteristics yielded rather secondarily by absorption of, or exchange with the foreign ions or others.