Distributed antireflection (AR) layers with different composition ratios of ITO and ${\mathrm{SiO}}_2$ formed on an ITO electrode of GaN-based LEDs provide substantial enhancement in light-extraction efficiency. By using the coradio frequency magnetron sputtering deposition, four $50\mathrm{nm}$ thick AR layers with graduated refractive indices were fabricated. The effect of the AR layers on enhancing the efficiency of the LED device was analyzed by electroluminescence (EL) and I-V measurements. As a result, the EL intensity of the LED device grown on the patterned sapphire substrate with AR layers was increased by up to 13% compared to the conventional patterned sapphire substrate-applied LED device without AR layers at a drive current of $20\mathrm{mA}$ . The AR layers on top of the LED device gradually changed the refractive indices between ITO ( $n=2.1$ ) and air ( $n=1.0$ ), which minimized the total internal reflection of generated light. And no degradation in the electrical characteristic of the LEDs was observed according to the I-V measurements.