A high-level region and a low-level region are formed on a surface of a nonmagnetic base member, in which high-level region is formed a ferromagnetic thin film pattern which corresponds to a preformat information signal, in such a structure that a flow promoting shape of such a shape (e.g., smooth curved shape, polygonal shape) that inhibits the stagnation of a flow of a detergent to promote the flow in order to prevents sticking and residing of foreign matter contained in the detergent is formed at an area where the detergent is liable to stagnate in the high-level region, i.e. at an inner radial portion of a disk-shaped mater information carrier.