In establishing regional industrial policies, it is important to understand the clustering structure of regional industries. In particular, in order to promote a smart specialization strategy that establishes a growth strategy that reflects regional characteristics, the degree of specialization and diversification of the regional industry must be simultaneously identified. The related variety index, which has been widely used in the past, measures the degree of diversification of related industries on a regional basis and explains the macroscopic structure of regional industries. However, through regional analysis, it was impossible to identify specialized areas within a region where various industries are concentrated and to determine the degree of diversification within specialized industries. Accordingly, this study proposed Scope Cluster Index, which measures the related variety index at the level of regional manufacturing industries and measures the relative level compared to the national level, as an indicator for regional industrial structure analysis. The Scope Cluster Index has a value greater than 1 as the value chain of the region's key industries is more balanced and diversified compared to the national average. This study divided the regional industrial structure into four types based on the Scale Cluster Index based on the Location coefficient and the newly proposed Scope Cluster Index as two axes. This study applied the indicators and type classifications proposed above to the manufacturing industry in the Southeast region to determine the degree of diversification of regional industries by industry type and analyzed the different agglomeration structures by regional manufacturing industry. In addition, the relationship between Scope Cluster Index and the performance of local industries was found to be positive(+). This study concludes by presenting a regional development strategy that can be derived as a result of applying the Scope Cluster Index to the southeastern region's manufacturing industry and discussing the usefulness and limitations of the Scope Cluster Index.