Isotropic chemical wet etching of n-Si (110) was investigated in KOH solution under applied voltage. It was shown that isotropic etching was achieved in 32wt% KOH at 110°C when applied voltage to the Si wafer was greater than 0.6V (vs. Pt electrode), while the Si wafer was etched anisotropically without applying voltage. This result shows that the etching property, isotropic or anisotropic, is varied by applying voltage. The etching rate of Si (110) for isotropic and the anisotropic etching were 0.1μm/min and 9μm/min, respectively at 110°C. In addition, the etching rate of the isotropic etching did not dependent on the applied voltage when using n-Si. The cause of the isotropic etching in KOH solution originated from etching through the anodic oxide layer formed on the Si surface due to XPS-analysis and the temperature dependence of the etching rate.