[Purpose] The purpose of the present study was to analyze the correlations of the thicknesses of the transversus abdominis muscle (Tra) and the internal obliquus abdominis muscle (Io) with static lumbar stability (SLS), dynamic lumbar stability (DLS), and balance. [Subjects] The subjects of the present study were 40 female university students who had no physical defects or pain. [Methods] The thicknesses of Tra and Io muscles were measured using an ultrasonic imaging diagnostic unit. SLS and DLS were measured using a Pressure Biofeedback Unit (PBU), and Weight Distribution Indexes (WDI) and stability scores (SS) were measured using a balance measuring unit. [Results] As the thickness of the Tra increased, SLS, DLS, WDI, and SS improved. As SLS improved, DLS and WDI were also improved. [Conclusion] To improve lumbar stability and balance, training is needed in order to increase the muscle mass of the transversus abdominis muscle.