Wire electrochemical machining (WECM) using bipolar pulse current with scanning wire electrode can be effectively applied to mirror-finish the wire electrical discharge machined surfaces of stainless steel. However, highly alloyed materials with insoluble precipitates such as cold tool steel and nickel-based superalloy are hard to finish, due to their non-uniform phase. This study aimed to finish these highly alloyed materials, by optimizing the duty factor. The machined depth, surface roughness, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) observation, bending strength, and edge roundness of WECMed surface of these materials were investigated. As a result, the duty ratio of 30% for cold tool steel and 40% for Inconel 718 were most effective to smoothen the surface uniformly. Furthermore, the shape accuracy of WECMed surfaces of small holes and thicker workpieces was also reviewed. The inner surface of small holes made in stainless steel with 0.5 mm in diameter was finished to surface roughness of Ra 0.088 µm, which is almost the same roughness as obtained with plane surfaces. Even a workpiece of 120 mm thickness was finished successfully with a straightness smaller than 2 µm.