To suppress backlash of a slider in a cutting tool in which the slider is sliaiably loaded in a recessed groove formed in the conical tool body to permit a cutting edge-tip to be slid.

A spacer 8 provided with a serration groove 8a is interposed between a slider 7 and one wall face 6a of a pair of wall faces 6a, 6b of a recessed groove 6 so that it can be freely loaded and unloaded. A serration groove 7a engaging the serration groove 8a is formed on one side face of the slider 7 abutting against the spacer 8, while a recessed part 21 of V-shaped cross-section, which is recessed toward one side face side of the slider, is formed on the other side face of the slider 7, and a pair of wedge members 22, 22, respectively in close contact with a pair of slopes 21a, 21a of the recessed part 21 formed into V-shape. are interposed between the other side face of the slider and the other wall face 6b of the recessed groove 6 in state where they are energized by a coiled spring 23 in the direction in which they move apart.