To design a slip stopper to prevent an infant seated in an infant seat from slipping down with reliability without physically burdening it over a longer period of its growth and to b e stored away in smaller space while not used.

A seat cushion 17 has a bottom 17a, a back rest part 17b seriated to the bottom 17a, and a footrest 17c on which a piece of plain cloth is sewn as a coming off preventing cloth 17e over not only the front side but also the right and left sides. The cushion 17 is provided at inner forward portions of its armrest covers 17d with pockets 17f that are open at their rear sides by means of hook-and-loop fasteners. The coming off preventing cloth 17e is formed at its appropriate position with a second crotch-belt hole 17n, in which a crotch belt is inserted.