PURPOSE: To obtain a conjugate yarn having excellent heat-insulation and suitable for winter ware such as sweater by spinning a yarn in such a manner as to form a core part composed of filaments of e.g. polyamide containing a specific amount of fine metal particles and a sheath part composed of animal hair fiber.

CONSTITUTION: The objective conjugate yarn is produced e.g. by melting a polyester or a polyamide, adding ≥0.5 wt.% of fine particles of one or more kinds of metals selected from copper, silver, aluminum, nickel and chromium and having a particle diameter of preferably 0.1-0.5μm to the molten polymer immediately before extrusion and spinning animal hair fiber such as wool and cashmere in such a manner as to form an outer circumferential part with the animal fiber around the core part formed by the above process.