To obtain a disk brake rotor applicable, in particular, to large-sized truck, having high properties, and reduced in costs by specifying the composition of elements of flake graphite cast iron.

Flake graphite cast iron is used as a material suitable for disk brake rotor; however, it is necessary to improve thermal conductivity and lower Young's modulus in order to improve heat check resistance. The increase in C content suffices for the above purpose but deterioration in strength is brought about. Cr, therefore, is added, but the increase of the additive quantity of Cr causes formation of chill at the time of casting and deterioration in machinability. Accordingly, it is necessary to synthetically control the content of Cr and further the contents of Mn and Cr in order to facilitate control for preventing chilling, reduce costs, and produce the material suitable for use, in particular, in a large-sized truck. That is to say, Mn content and Cr content are controlled to <0.5% and >0.5-1.5% by weight ratio, respectively. Further, the sum total (α) of the contents of Mn and Cr is controlled so that 0.5%≤α≤1.5% by weight ratio is satisfied.