A rocker arm for use in an internal combustion engine. The rocker arm has a portion abutting an opponent mechanical component, and at least the portion is formed of a cast iron consisting of from 2.5 to 3.7 wt % of carbon; from 1.0 to 2.0 wt % of silicon; from 0.5 to 1.0 wt % of manganese; from 10 to 20 wt % of chromium; from 0.3 to 0.7 wt % of nickel; not more than 0.3 wt % of phosphorus; not more than 0.1 wt % of sulfur; and balance iron and impurities; Carbide mainly containing chromium is uniformly precipitated from at least one of pearlitic and martensitic matrix in the cast iron.
