Abstract: A CMP pad conditioner including: (a) a disk-shaped substrate having a working surface which is provided by one of its axially opposite end surfaces and which is to be brought into contact with the CMP pad; and (b) abrasive grains which are fixed to the working surface. The substrate includes a radially inner portion and a radially outer portion which is located radially outwardly of the radially inner portion. The working surface in the radially outer portion is inclined with respect to the working surface in the radially inner portion, such that a thickness of the radially outer portion as measured in an axial direction of the substrate is reduced as viewed in a direction away from an axis of the substrate toward a periphery of the substrate. A ratio of an outside diameter of the radially inner portion to an outside diameter of the substrate is 60-85%.