PURPOSE: To obtain a fancy yarn composed of core yarn and sheath yarn and having excellent fusiform shape and random length and thickness of individual parts by carrying out fluid-jet treatment of two or more strands of multifilament yarn while instantaneously controlling the feeding rate of yarn to the multifilament yarn.

CONSTITUTION: Two or more strands of multifilament yarn are subjected to a core/sheath conjugate processing by a fluid-jet treatment to impart bulkiness such as loops, entanglements and sags. In the above process, the feeding rate of the multifilament yarn to form the sheath yarn is instantaneously controlled to obtain a fancy yarn consisting of a conjugate yarn composed of a core yarn and a sheath yarn and having bulky parts and non-bulky parts alternately distributed in the direction of the length of the yarn, wherein said bulky part has fusiform shape formed by loops, entanglements, sags, etc., and the individual parts have random lengths in the direction of the yarn length.