A novel synchronizer ring for use in speed variators that is made of an iron-base sintered alloy and which has high strength and wear resistance while exhibiting good accommodation by the mating surface is disclosed. This synchronizer ring is made of an iron-base sintered alloy that contains 0.1-0.9 wt % C., and at least one optional element selected from among 0.1-6 wt % of at least one of Mn, Cr and Mo, 0.1-6 wt % of at least one of Ni and Cu, and 0.02-0.5 wt % B, the balance being Fe and incidental impurities (Si, S and P as incidental impurities being present in a total amount not exceeding 0.5 wt %), and which has a porosity of 0.05-5 vol %. The properties of this ring, notably its wear resistance, can be further improved by forming either a hard Ni-P compound layer or a nitrided layer on at least the surface of the above-specified sintered alloy which is to make sliding contact with a tapered cone.