A composite yarn which is composed of a core part comprising short fibers and a sheath part comprising a filament yarn constituted of synthetic fibers, wherein the fluff of the short fibers has penetrated into interstices among the filaments or twined therewith to unite the core part with the sheath part. The composite yarn has a specific gravity of 1.0 or higher which can be regulated. Also provided are a fishing line comprising the yarn and a process for producing the fishing line. The core-sheath structure is firm, and neither separation nor peeling substantially occurs between the core part and the sheath part. This fishing line is an ideal fishing line excellent not only in handleability but in strength, weatherability, and water resistance.
