A green-emitting phosphor is activated by cerium and terbium and is represented by the general formula:(Re.sub.1-a-b-3c Tb.sub.a Ce.sub.b A.sub.3c).sub.2 O.sub.3.mP.sub.2 O.sub.5.nSiO.sub.2wherein Re is at least one member selected from the group consisting of yttrium, lanthanum, and gadolinium; A is at least one member selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs); and a>0, b>0, c>0, 0 0, and n>0.The green-emitting phosphor of the invention may be widely applied to fluorescent lamps for copying machine light sources, or high luminous efficacy and high color rendering property fluorescent lamps such as three peak emission system fluorescent lamps.