To provide a boring tool which is excellent in chip treatment performance and machining accuracy of a machined hole, dispenses with grinding of a nick whenever a cutting blade is re-sharpened, and exerts excellent tool life.

There is provided a method of producing a tip 100 which has its cutting blade portion 15 formed of an ultra-high pressure sintered body such as a diamond sintered body, and a cubic boron nitride sintered body, and is to be mounted on the boring tool 200. The method is composed of a step in which part of the cutting blade portion 15 of the tip 100 before being mounted on the boring tool 200, is cut away in an area from the cutting blade portion 15 toward a rake face 11 by electric discharge machining such as wire cutting, laser machining, and electron beam machining, to form a slit 10 that penetrates in a thickness D direction of the tip 100 and has a length longer than the thickness D in a rake face 11 direction.