Abstract: A manganese-based damping alloy having stable damping properties; a process by which the damping alloy can be obtained without fail; and a damping part or vibration-proof product comprising or employing the damping alloy. A damping alloy made up of from 16.9 to 27.7 wt% copper, from 2.1 to 8.2 wt% nickel, from 1.0 to 2.9 wt% iron, 0.05 wt% or less carbon, 0.06 wt% or less oxygen, 0.06 wt% or less nitrogen, and manganese and unavoidable impurities as the remainder. Due to this constitution, nonmetallic inclusions such as carbides generate in a reduced amount and the manganese-based alloy can be pure. Consequently, the formation of a twin-crystal structure during heat treatment is accelerated and factors which inhibit the twin-crystal structure from moving upon stress imposition are diminished, whereby damping properties can be improved.