This research classified hospital specialization strategy types through cluster analysis, analyzed fitness of hospital specialization strategy types for external environment or organizational structure, and examined relation between hospital specialization strategy types and organizational performance. This research surveyed 1,437 hospitals which have more than 30 patient`s bed and practice national health service in Korea. Specifically, this research divided into two part : external fit - analysis of relation between external environment and specialization strategy, internal fit-analysis of relation between organizational structure factors and specialization strategy. also, as the organizational performance for achieving specialization strategic purpose, not only the productivity, efficiency, profit but also the medical quality was considered. In case of external fit, many hospitals chose integration type if there are a lot of competitive hospitals and regional population. Particularly, if there are many competitive hospitals, concentration type is chosen. In contrast, if there are many doctors in the region, differentiation type is chosen. In case of internal fit, according to organization type and patient`s bed number, hospitals chose different types. If it is a general hospital and has a few bed number, generalization or concentration type is chosen. Tertiary hospital or the hospital with many patient`s bed chose differentiation type. According to the number of specialists, if there are a few specialists, generalization or concentration type is chosen. If there are many specialists, differentiation type has high fitness for the hospital. In relation to strategy types and organizational performance, differentiation type has best result. Differentiation type has a good result in 7 items out of 11.