To form a seat side pocket which is easy to be fabricated as a pocket body, whose structure can be simple, which is easy to take out things and to put them in, and whose appearance can be kept good restraining the pocket body from swelling outward.

A concave part 12 demarcating a chamber for containing things is provided on the side part of a pad, an outer covering material 10 cut in the prescribed plane shape is applied to the side of the trim cover T and sutured flatly as a bag-like pocket body P with an opening 11 for taking things in or out, the pocket body P is located at the concave part 12 of the pad, and an opening width 14 for taking things in or out is formed as the pocket body P maintainable in the cavity of the concave part 12.