The present disclosure relates to a manufacturing method of high-strength flake graphite cast iron, the high-strength flake graphite cast iron manufactured by the method, and an engine body including the cast iron, and more particularly, to flake graphite cast iron and a manufacturing method thereof, wherein the flake graphite cast iron has a uniform graphite shape and low probability of forming chill and has high tensile strength of at least 350 MPa and excellent workability and fluidity by controlling the content of manganese (Mn) and a trace of strontium (Sr), which are included in the cast iron, within a specific ratio.