Abstract: In order to prevent a cutting tool from being detached from the holding device towards a bladed part-side when holding a standard cutting tool in the holding apparatus, a focus was placed on a diameter of a shank of the standard cutting tool which is larger than that of a bladed part-side cylindrical portion. A pressing portion pushes a retaining ring along a slope in a tool inserting hole towards its base end side so that an outer periphery of the retaining ring shrinks and an inner diameter of the retaining ring becomes smaller than the diameter of the shank.