Disclosed herein are an apparatus and method of adjusting a clearance of an electronic brake, in which a clearance between a pad and a rotor is appropriately adjusted according to a vehicle traveling situation. If the entry condition of a clearance adjustment section during stoppage is satisfied, clearance adjustment is performed to move pads of an electronic brake away from a rotor by a rearward-movement adjustment distance during stoppage, enabling rapid braking-release so as not to prevent a driver from starting a vehicle due to brake failure. In addition, if the entry condition of a clearance adjustment section during traveling is satisfied, clearance adjustment is performed to move the pads forward or rearward according to a wheel slip value. The clearance adjustment during traveling is limited to the case of straight traveling, to prevent misjudgment due to wheel slip caused during cornering.