This study proposed three types of situational leadership theories based on levels of analysis, demonstrated that each type has a competitive relationship with existing leadership theories—namely, average leadership style (ALS) theory, vertical dyad linkage (VDL) theory, and individualized leadership (IL) theory—in terms of variable relationships, and attempted to determine which among the three types of situational leadership theories and existing leadership theories is more valid. Data collected from 120 individuals across 36 groups were analyzed, and the results indicated that the three types of situational leadership theories were not valid; moreover, both the average leadership style theory and vertical dyad linkage theory were also found to be invalid. However, the analysis results showed that individualized leadership theory was valid, suggesting that subordinates' maturity does not moderate the relationship between leader behavior and performance, but rather has a significant relationship with both leader behavior and subordinate performance. These research findings were discussed from the perspective of social exchange theory, and the limitations of this study were also addressed.