The rapid diffusion of the Internet and the emergence of Internet banking are bringing about significant changes across the banking industry. In particular, as the number of Internet banking users has increased rapidly in recent years, interest in Internet banking has been growing. For banks to strategically expand their Internet banking services, it is necessary to understand customer Internet banking usage behavior. Therefore, this study sought to identify the factors influencing Internet banking usage behavior by empirically analyzing customer Internet banking usage behavior based on the Theory of Planned Behavior. A research model was established based on the Theory of Planned Behavior and empirically analyzed using structural equation modeling. The empirical analysis confirmed that attitude toward Internet banking, subjective norms (social pressure), and perceived behavioral control affect Internet banking usage intention, and that behavioral beliefs about Internet banking (Σbᵢeᵢ), normative beliefs about Internet banking (Σnbᵢmcᵢ), and control beliefs about Internet banking (Σcbₖpfₖ) affect attitude toward Internet banking, subjective norms regarding Internet banking, and perceived behavioral control over Internet banking, respectively. This provides empirical evidence that the Theory of Planned Behavior can be applied to predict and explain Internet banking usage behavior.