Commercially available n-type 6H-SiC wafers were etched in aqueous KOH solution by an electrochemical method. We varied the etching conditions, such as KOH concentration, temperature, UV illumination and current density, and then we observed morphologies of etched surface and etched depth. The flattest etched surface in the present work was obtained in 1 wt.% KOH solution at temperature of 50-55degreesC under UV illumination with a current density of 1 mA/cm(2). We also fabricated a patterned structure by this etching method.