According to the present invention, a down product having a joining pattern line for separating chambers without creating stitch holes or damaging fabric, can be manufactured by: printing a heat-reactive adhesive liquid on the inner surface of a lining, any kind of mesh member, and/or shell, into a specific printing pattern and then drying same; bonding the lining, the any kind of mesh member, and the shell; compressing same into a compressing pattern that is identical to the printed pattern; and then high-frequency heating the compressing pattern to join the lining, the any kind of mesh member, and the shell using the adhesive liquid. According to the present invention, through a high-frequency bonding technique using the heat-reactive adhesive and/or a bond-first cut-later technique in which double-layer fabric is first manufactured by forming chamber-dividing lines and then cutting same, down products can be manufactured to have inner seams having excellent adhesive force and durability and bonding pattern
