Abstract: An object of the present invention is to provide a cutting method and apparatus and a rib electrode for electric discharge machining which can cut a rib portion of a workpiece efficiently and accurately. For this purpose, a cutting tool 11 having cutting edges 23a, 23b extending in parallel or extending along two straight lines diverging toward the forward end in the same plane is prepared. The cutting tool 11 is arranged with respect to a workpiece W such that the two cutting edges 23a, 23b engage with the two opposed side surfaces of the rib portion R of the workpiece W. The cutting tool 11 is moved relative to the workpiece W along a desired machining path, to thereby cut the two side surfaces of the rib portion R of the workpiece W at one time.