This paper is an empirical study about What the determinants of capital structure of Korean representative public firms are since 2000. The results of empirical analyses are summarized as below. Firstly, the collateral value of tangible assets positively contributes to debt financing of public firms. Growth represented by yearly total asset change also positively contributes to debt financing as traditional 'Trade-off & Agency theory' asserts. However, profitability & liquidity negatively contributes to debt financing as 'Pecking order theory' asserts . In addition, non-debt tax shield using depreciation & amortization is negatively associated with debt financing, which means depreciation & amortization are partially used as tax shield apart from the typical debt tax shield of interest costs.