Abstract: A master cylinder body including a cylindrical-shaped inner section of uniform wall thickness formed as by die-casting and an outer section cast on the inner section around the periphery thereof. The extreme simplicity in configuration of the inner section enables it to be formed with no casting defects such as shrinkage cavities which may result in oil leakage therethrough. The inner section and the outer one cast thereon become solidly fused together at the cylindrical interface therebetween as long as the materials used are of the same metallurgical type. Formation of a multitude of annular or helical ridges on the outer periphery of the inner body section further ensures the solid interconnection between the two body sections.