Abstract: A separator of the invention is designed to remove foreign materials, such as small stones, included in granulated materials, such as red beans, having smooth outer surfaces. The separator is formed of a supplying section, and a separating section for receiving the granulated materials with the foreign materials from the supplying section and separating the foreign materials from the granulated materials. The separating section includes at least one pair of elongated rollers formed of first and second rollers, which are arranged parallel to and at a predetermined distance spaced apart from each other. The first roller has a spiral projection on an outer surface thereof. When the granulated materials with the foreign materials are supplied onto one end of the pair of the rollers, the foreign materials are caught between the rollers and dropped downwardly, while the granulated materials are transferred to the other end of the rollers by the rotating spiral projection and are collected.