A wire electric discharge machining method of forming an ultra-hard material (101, 102) that is fixed to a cutting tool, into a cutting blade (101', 102') by performing electric discharge machining on the ultra-hard material according to a machining program by using a wire electric discharge machine having a taper machining function, wherein the wire electric discharge machine is configured such that the cutting tool can move relatively, in two mutually orthogonal axis directions, with respect to a wire electrode that is stretched by an upper wire guide and a lower wire guide, and a touch sensor is mounted to the upper wire guide, and the wire electric discharge machine further has a rotating shaft to which the cutting tool is removably mounted, characterised in that the wire electric discharge machining method comprises: generating a measurement program for setting, along a machining path instructed by the machining program, each point of a plurality of divisional positions between the origin and the endpoint of the machining path, as a measurement point at which contact between the ultra-hard material (101, 102) and a probe end section of the touch sensor is detected at a rotation center height of the rotating shaft; positioning the probe end section of the touch sensor at the measurement point on the basis of the generated measurement program; causing the rotating shaft, to which the cutting tool is mounted, to rotate in a direction in which a face of the ultra-hard material (101, 102) being fixed to the cutting tool, that forms a tool rake face (101'a) comes into contact with the probe end section of the touch sensor; reading rotating shaft coordinate information for which the face of the ultra-hard material that forms the tool rake face (101'a) at the measurement point is at the rotation center height of the rotating shaft, on the basis of a detection signal from the touch sensor obtained when the face that forms the tool rake face comes into contact with the probe end section of the touch sensor; storing path coordinate position information, being coordinate data in the two orthogonal axes at the measurement point, as well as the read rotating shaft coordinate information; regenerating a machining program from the path coordinate position information and the rotating shaft coordinate information that are stored; and forming a cutting blade (101', 102') through wire electric discharge machining of the ultra-hard material (101, 102) by the wire electrode that is stretched by the upper and lower wire guides (14, 15), according to the regenerated machining program. generating a measurement program for setting, along a machining path instructed by the machining program, each point of a plurality of divisional positions between the origin and the endpoint of the machining path, as a measurement point at which contact between the ultra-hard material (101, 102) and a probe end section of the touch sensor is detected at a rotation center height of the rotating shaft; positioning the probe end section of the touch sensor at the measurement point on the basis of the generated measurement program; causing the rotating shaft, to which the cutting tool is mounted, to rotate in a direction in which a face of the ultra-hard material (101, 102) being fixed to the cutting tool, that forms a tool rake face (101'a) comes into contact with the probe end section of the touch sensor; reading rotating shaft coordinate information for which the face of the ultra-hard material that forms the tool rake face (101'a) at the measurement point is at the rotation center height of the rotating shaft, on the basis of a detection signal from the touch sensor obtained when the face that forms the tool rake face comes into contact with the probe end section of the touch sensor; storing path coordinate position information, being coordinate data in the two orthogonal axes at the measurement point, as well as the read rotating shaft coordinate information; regenerating a machining program from the path coordinate position information and the rotating shaft coordinate information that are stored; and forming a cutting blade (101', 102') through wire electric discharge machining of the ultra-hard material (101, 102) by the wire electrode that is stretched by the upper and lower wire guides (14, 15), according to the regenerated machining program.