To investigate surface free energy of rubbed polyimide surfaces as a function of the rubbing strength, we measured the contact angle of distilled water and methylene iodide on the polyimide surfaces. For this purpose, a main-chain-type and two side-chain-type polyimides were used. The dispersion force (gamma(d)) and the polar force (gamma (P)) Of the rubbed polyimide surfaces was measured. The rubbing induced polarity on the polyimide surfaces. Also, polar forces contributed to form a pretilt angle of liquid crystals on the rubbed polyimide surfaces.