We demonstrate electro-optic tuning of an on-chip lithium niobate microresonator with integrated in-plane microelectrodes. First, the metallic microelectrodes were fabricated on the substrate using a femtosecond laser. Then high-Q lithium niobate microresonator located between the microelectrodes was further fabricated by femtosecond laser direct writing accompanied by focused ion beam milling. Thanks to the efficient design, a high electro-optical tuning coefficient of 3.41 pm/V has been obtained.