Owing to several contributing factors, continuation of exercise therapy is difficult for patients with type 2 diabetes. One potential factor that has not been well examined is the influence of muscle strength on regular exercise behavior. We examined the relationship between regular exercise behavior and knee extension force (KEF) in 1,442 patients with type 2 diabetes. In sex-specific univariate analysis, KEF was significantly higher in patients who regularly exercised than in patients who did not regularly exercise. However, age, but not exercise behavior, was significantly different between KEF quartiles. Accordingly, KEF and age might strongly influence exercise behavior. In the multivariate analyses using age and other parameters as covariates, KEF was a significant explanatory variable of regular exercise in both men and women, suggesting that muscle strength could influence regular exercise behavior.