An alloy to be surface-coated, which can keep excellent hardness of 58HRC or above even when the amount of an alloying element added is reduced or even when the alloy is heated to a temperature of as high as 400 to 500° C.; and sliding members produced by forming a hard film on the surface of the alloy. An alloy to be surface-coated, the surface of which is to be covered with a hard film, which alloy contains by mass C: 0.5 to 1.2%, Si: 2.0% or below, Mn: 1.0% or below, Cr: 5.0 to 14.0%, Mo+1/2 W: 0.5 to 5.0%, and N: more than 0.015 to 0.1% with the balance being Fe and impurities, preferably such an alloy which contains by mass C: 0.6 to 0.85%, Si: 0.1 to 1.5%, Mn: 0.2 to 0.8%, Cr: 7.0 to 11.0%, Mo+1/2 W: 1.0 to 4.0%, and N: 0.04 to 0.08%.