PURPOSE: To obtain the subject interlaced yarn, having homogeneous and soft bulge and excellent in bulky feeling by subjecting plural multifilament yarns having respective specific single filament denier and shrinkage factor in boiling water to relaxing heat treatment.

CONSTITUTION: (A) Multifilament yarn having ≤0.75 denier single filament size after drawing and ≤10% shrinkage factor in boiling water and (B) multifilament yarn having 0.8-2.0 denier single filament size and ≥20% shrinkage factor in boiling water are paralleled in or after drawing, interlaced in a fluid interlacing nozzle to ≥50 interlacing degree and then subjected to relaxing heat treatment at 10-20% relaxing ratio to afford the objective interlaced yarn having respective ≤0.8 denier and 1.0-2.5 denier sizes of filaments in the sheath and the core parts at (1:1)-(10:1) weight ratio of filaments in the core part to the sheath part, ≥60 loops or slacks/m protruding to ≥0.3mm length and 2-10% shrinkage factor in boiling water.