Provided are an alloy for spring, a plate material for spring, and a spring member, all of which are high in mechanical strength, also high in fatigue strength, and excellent in corrosion resistance. An alloy for spring of the present invention includes, as composition in terms of weight ratio, 28 to 42% Co, 10 to 27% Cr, 3 to 12% Mo, 15 to 40% Ni, 0.1 to 1.0% Ti, 1.5% or less Mn, 0.1 to 26.0% Fe, 0.1% or less C, and inevitable impurities, and at least one kind selected from 3.0% or less Nb, 5.0% or less W, 0.5% or less Al, 0.1% or less Zr, and 0.01% or less B.