A method of manufacturing and a device for manufacturing a partial split-fiber fiber bundle and a partial split-fiber fiber bundle obtained are characterized by piercing a fiber splitting means provided with a plurality of protruding parts into a fiber bundle formed from a plurality of single fibers while making the fiber bundle travel along the longitudinal direction thereof and creating a split-fiber processed part, forming entangled parts where single fibers are interlaced at contact parts with the protruding parts in at least one split-fiber processed part, thereafter pulling the fiber splitting means out of the fiber bundle, and after passing through an entanglement accumulation part including the entangled parts, once again piercing the fiber splitting means into the fiber bundle.