Fatigue crack propagation tests for the brake disc cast iron were conducted for investigating fatigue crack propagation rate(da/dN), crack propagation path and fracture toughness($K_c$) of the material. The threshold stress intensity factor range, ${Delta}K_{th}$, was found to be about $6MPa{sqrt{m}}$ at the stress ratio of R = 0.1. Also, fracture toughness value was determined to be $24.7MPa{sqrt{m}}$. Irregular fatigue fracture surfaces were observed, indicating that fatigue crack growth occurred at the interface between randomly scattered flak graphite and ferrite, where the interfacial strength was relatively weak.