A polybenzazole fiber, staple fiber, spun yarn or woven or knit fabric, comprising an organic pigment contained in the fiber, the organic pigment being one having -N= and/or NH- in its molecular structure, such as any of perinone and/or perylenes, phthalocyanines, quinacridones and dioxazines, the organic pigment being highly thermally stable one whose thermal decomposition temperature is 200˚C or higher, the organic pigment being soluble in a mineral acid, which polybenzazole fiber, staple fiber, spun yarn or woven or knit fabric exhibits a strength retention, measured after exposure to xenon radiation for 100 hr, of 50% or higher and a tensile strength retention, measured after exposure in an atmosphere of 80˚C and 80% relative humidity for 700 hr, of 85% or higher. The polybenzazole fiber, staple fiber, spun yarn or woven or knit fabric can find application in a code for rubber reinforcement, a sheet or rod for cement/concrete reinforcement, a composite material, a sail cloth, a rope and a bullet and knife proof vest.