A simple natural lithography process was employed to roughen the indium tin oxide (ITO) window layer to improve the performance of an InGaN-GaN light emitting diode (LED). In this process, a photoresist layer was used as a mask for inductively coupled plasma (ICP) dry etching. The photoresist was distorted during the ICP etching process. As the etching time increased, the distorted shapes of the photoresist were transferred to the ITO surface. The roughness of the ITO surface can be easily controlled by the thickness of the photoresist mask. Moreover, the performance of LEDs increased with the thickness of the photoresist mask.