Biodiversity is associated with functional protection, adaptation to external conditions, and ecosystem resilience. Therefore, maintaining forest ecosystems with high biodiversity is essential for improving resistance and resilience to disturbances. In addition to the ecological factors influencing forest ecosystems, various socio-economic factors associated with forests can influence the ecosystem. However, socio-economic impacts on forest biodiversity have rarely been addressed. In this study, we investigated whether tree species diversity (TSD) of forest stands varies with ownership status (national vs. private forests). In addition, selected ecological (stand characteristics, site conditions, and climate) and socio-economic (regional forest management sectors, population, forestry population, forest coverage, and forestry income) factors influencing TSD were determined using data from the National Forest Inventory in South Korea. National forests had higher TSD than private forests, reflecting differences in management objectives. Among ecological factors, stand structural diversity (SDivI) was the most influential in both national and private forests. Socio-economic factors, such as population, forest coverage, forest income, and forest management bodies, significantly influenced the TSD, although the impact was smaller compared to ecological factors. Our results suggest that securing stand growth and development is essential for increasing stand structural diversity, which leads to an increase in TSD. Furthermore, our study shows that socio-economic factors can influence forest conditions over time. To better understand the factors influencing the state of forests and manage forests sustainably in the future, collaborative research bridging ecological and sociological fields is necessary.