Abstract: A double layered yarn having a sheath and core structure is prepared through a roving process, drawing process or fine spinning process. The sheath portion of the yarn is composed of staple fibers which have a high thermal shrinkage in boiling water of at least 5%, and the blended fiber ratio of which is between 50% and 25%. The core portion of the yarn is composed of staple fibers which have a property being spontaneously extensible, and the blended fiber ratio of which is between 25% and 75%. The double layered yarn is subjected to a heat treatment in hot water, and a bulky spun yarn which comprises staple fibers A and B is obtained. The staple fibers A are concentrated toward the inside of the bulky spun yarn after they are shrunk. The ends of staple fibers B are held within the inside of the bulky spun yarn, and the intermediate portions of fibers B are bulged as a loop from the body portion of the bulky spun yarn, after the fibers B are spontaneously extended.

Abstract: A roving formed from a first kind of staple fibers, each of which is at least 3 denier, is interposed with a randomly mixed sliver formed from a second kind of staple fibers, each of which is between 1.5 denier and 3 denier, and a third kind of staple fibers, each of which is at most 1.5 denier, the thermal shrinkage of the second kind of staple fibers being higher than that of the third kind of staple fibers. The roving and the randomly mixed sliver are twisted together so that the sliver wraps around the roving in order to form a double layered roving. After the double layered roving is subjected to fine spinning, it is then subjected to a heat treatment. As a result, a multi-layered bulky spun yarn is obtained.