To provide wear resistant steel which has excellent delayed fracture resistance.

The steel has a composition containing, by mass, 0.05 to 0.40% C, 0.1 to 0.8% Si, 0.5 to 2.0% Mn, 0.1 to 2.0% Cr, 0.005 to 0.10% Ti, 0.0005 to 0.005% B, 0.005 to 0.10% Al, and ≤0.005% N, and the balance iron with inevitable impurities. The steel has a martensitic structure. Also, an old austenite grain extension degree expressed by the ratio of the old austenite grain size in the rolling direction (dL) of the steel to the old austenite grain size in the thickness direction (dZ) of the steel, i.e., (dL/dZ) is ≥2.