To provide a tool for use in conditioning, which is easy to control processes and also can improve a service life of the tool.

The polishing tool includes a rigid substrate having a planar circular surface, on which a group of cutting edges 31 with a flat top face of a limited area positioned within a certain level for the circular surface are arranged in a grid state comprising two intersecting sets of parallel lines 41 and 42. Each cutting edge 31 is made of sintered diamond having a rectangular cross section (horizontal cross section) vertical to an axis of the tool on the top and also having a longitudinal ridge extending in the axial direction. The cutting edge 31 is formed in a plurality of polishing islands with an area limited as a group. The polishing tool includes the plurality of polishing islands which are regularly disposed on concentric circles with respect to the rotation center of the tool at a constant spacing, and is suitable for dressing a CMP pad.