To provide a machining method suitable for machining even a hard material with fine dimensional accuracy, surface roughness, and efficiency.

This method is provided with a tool in a substantially axisymmetric shape which is composed of a conductive sintered cubic boron nitride, a sintered diamond, or a conductive vapor phase synthesized diamond, a workpiece formed of a conductive hard material with hardness equal to or lower than that of the tool, a rotating means rotating the tool around the axis of symmetry, a driving means changing the relative position between the workpiece and the tool, and an electricity supply means applying a voltage between the workpiece and the tool. The voltage is applied between the workpiece and the tool by the electricity supply means, and the tool rotated by the rotating means and the workpiece are moved relatively while being approximated by the driving means, thereby dressing the tool while subjecting the workpiece to electrical discharge machining. Then, voltage application by the electricity supply means is stopped, and the electric discharge surface of the tool rotated by the rotating means is contacted with the electric discharge-machined surface of the workpiece by the driving means, thereby grinding the electric discharge-machined surface of the workpiece.