A partially separated fiber bundle having a surface of a reinforcing fiber coated with a sizing agent containing a water-soluble polyamide-based resin, in which a separated fiber section consisting of a plurality of separated fiber bundles and an unseparated fiber section are provided alternately along a longitudinal direction of the reinforcing fiber bundle consisting of a plurality of single yarns, wherein the reinforcing fiber bundle contains 600 fibers/mm or more and less than 1,600 fibers/mm of fibers per unit width while the reinforcing fiber has a drape level of 120 mm or more and 240 mm or less.