A diamond tool for the mirror-finish cutting of non-ferrous materials and a method of manufacturing the same are provided. The diamond tool has a main cutting edge and minute side cutting edges formed at the opposite ends of the main cutting edge so as to intersect the main cutting edge at an angle. The dept .DELTA. of chamfer of the side cutting edge is 1.5 to 5 times the depth of tears formed in the machined surface (0.1 .mu.m.ltoreq..DELTA..ltoreq.1 .mu.m) and the length l.sub.2 of the side cutting edged is 1.5 to 10 times the feed of the diamond tool (0.02 mm.ltoreq.l.sub.2 .ltoreq.0.8 mm). The rake face of the diamond tool comprises two rake faces and two side rake faces. A tool grinding surface plate for manufacturing the diamond tool has a flat surface for grinding the rake faces, and a circumferential tapered surface for grinding the side rake faces. The end relief surface and the rake face of the diamond tool is in the (001) zone of the single crystal diamond tip thereof, and the crystal orientation of the end relief surface is in the range of (150) and (010) or a crystallographic equivalent.