PURPOSE: To obtain a surface hardened steel having wear resistance on one side face by pouring molten steel having the prescribed composition into a mold, which has a rectangular cross section and can be cooled only at one side face, cooling from one side face forming the concentrated part on the other side face and hot-working after casting an ingot.

CONSTITUTION: After pouring the molten steel 2 into the mold 3, which has large short side in the cross section of horizontal direction as compared with the height, by cooling the mold bottom part, the molten steel 2 is unedirectionaly solidified from the bottom to the upper part and the raw material ingot developing the concentrated segregation part 1 on the whole face of mold top part is cast. Next, after rolling this ingot, in case of rapidly cooling by spray cooling water, as the composition, which has high quenchability on the upper face side of the ingot, is much contained, the one side surface is quech-hardened and the side surface hardened steel is obtd.