[Object] To provide a copper alloy synchronizer ring having an excellent plasticity/flowability resistance in a high calorific heat releasing environment. [Solving Means] A copper alloy synchronizer has a composition of Cu: 62.5 ~ 67.5 wt%, Al: 4.5 ~ 5.5 wt%, Ni: 2.7 ~ 3.7 wt%, Ti: 1.0 ~ 2.0 wt%, and Mn: 0.05 - 0.35 wt% and a balance of Zn and inevitable impurities, wherein, when Zn+(inevitable impurities)=ZN, a Zn equivalence represented by an equation {ZN+6x(Al-0.9)}/{Cu-1.3+ZN+6x(Al-0.9)} is in a range of 0.4 - 0.46, and wherein a basic structure of a copper alloy is a two-phase structure of ±-phase and ²'-phase, and wherein the ±-phase has a composition of Cu: 65 ~ 74%, Al: 2.5 - 4.5%, Ni: 0.5 - 2.5%, and Ti: 0.05 ~ 0.6%, and wherein the ²'-phase has a composition of Cu: 62 ~ 71%, Al: 3.5 - 6.0%, Ni: 0.3 - 2.3%, and Ti: 0.05 - 0.6%.
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