Survey data are analyzed Hayashi's third method of quantification and cluster analysis, to investigate the relationships between ambiguity in organizational practices and organizational effectiveness. The following main features are suggested : (1) Main organizational effectiveness on ambiguity in organizational practices are flexibility-adaptability and efficiency in organizational level, mutual trust-group harmony-stability in group level, and autonomy-exhibition of ability-development of ability in individual level. (2) Though organizational effectiveness regarding the ambiguity in organizational practices depends on the kinds of ambituigy based on different dimensions of ambiguity, flexibility-adaptability is connected with all kinds of ambiguity based on propensity for non-exclution of ambiguity.