In the magnetic-field-assisted finishing, grinding powder mixed with iron powder is placed inside a part and vibration is applied to the part under magnetic field. Effects of the process on deburring of step-wise holes and internal roughness of brass square pipes were examined. Rotation was given to the pipes with step-wise holes, while the magnetic poles were vibrated. Axial vibration was given to the square pipes, while the magnetic poles were fixed. Burr formed by drilling at internal edges was effectively removed by the process. Inside roughness of the square pipe was successfully finished to 0.023 μm Ra.