Disclosed herein is an ultra clean spring steel which contains inclusions easily elongated and broken into fine particles by hot rolling and which is easily adaptive to cold rolling and yields springs excelling in fatigue characteristics. The spring steel is characterized in that the wire contains oxide inclusions with a sulfur concentration no more than 10 mass % such that no less than 70% (in terms of numbers) of such inclusions, which exist in the outer layer outside one quarter of the diameter of the wire and have a width no smaller than 3 .mu.m, satisfies the formula (1) below, CaO+Al.sub.2O.sub.3+SiO.sub.2+MnO+MgO>80 (mass %) . (1)