Empirical studies have shown that as demand uncertainty increases, firms' cost structures tend to become more rigid. However, these studies analyzed firms facing different uncertainties together. Therefore, it is not ruled out the possibility that groups with extreme uncertainties influenced the results. In this study, we examine the relationship between uncertainty characteristics and cost structure by using the classification of firm life cycle. The results revealed that the introduction and decline stages, where the risk of demand upside is higher, show a more rigid cost structure with higher demand uncertainty. These results suggest that the results of the previous study's analysis may have been influenced by an extreme minority of groups.