Many countries have implemented fiscal decentralization as they accepted New Public Management(NPM) to their statecrafts for 20 years. However, other previous empirical studies, analyzing the relationship between fiscal decentralization and economic growth, have shown conflicting results. One of the reasons is that fiscal decentralization indices do not reflect the practical status of fiscal decentralization of the countries. The other reason is that many countries, which have different political and administrative circumstances, have implemented fiscal decentralization in their own ways. This study analyzed the effect of fiscal decentralization on economic growth of 34 OECD countries which were divided into 4 groups according to the level of Corruption Perception Index(CPI). Also, this study used CPI as a moderating variable in the latest cross-country data from 1990 to 2009.As a result, each fiscal decentralization of 4 groups had different influences on economic growth of them. Though 3rd and 4th group of countries were less corrupted than average countries, they had different results. The 3rd group of countries had a positive impact on economic growth, while the 4th group of countries which had the highest CPI than other groups had a negative impact. These results imply that the function of [integrity and [(a Economic growth)/(a Fiscal decentralization)]] is most likely the inverse U-shape. And this study implicate that ill-considered application of fiscal decentralization would be wrong.