Recently, many studies have shown that airfoils of which the leading edge had a shape with Humpback Whale flipper or sine wave had a increased lift coefficient and a decreased drag coefficient. In this research, wind tunnel experiments are performed to analyze the aerodynamic characteristics of the NACA4412 airfoil which has serrated Fowler flap and slotted flap with the sinusoidal leading edge. Results show that two serrated flaps with a specific sine wave shape have a larger lift-to-drag ratio and a smaller magnitude of pitching moment coefficient than the reference flaps. Therefore, the leading edge using a sine wave with the optimal amplitude and wavelength can improve aerodynamic behaviors of flaps.