To provide a portable seat light and convenient to carry, properly soft, and usable for a long time without having pain in the shin or the lower back.

A shock absorbing body 6 is roughly in the form of a triangular prism, its three side parts are round, its thickness is roughly equal to the height of knees, and it has such a hardness as to support the lower back when a user is seated on it. A drawstring purse-like bag body 4 contains the shock absorbing body 6 to cover it, and position a first side part 18 of the shock absorbing body 6 at a mouth part 30 of the bag body 4, so the form of the bag body 4 as it is contained, and as a mouth part 30 is tightened by drawstrings 8 roughly realizes the form of the shock absorbing body 6. When the user sits on it, having this portable seat 2 between the shins, it fits the legs and the lower back of the user, and softness is felt, while the lower back is tightly supported, so less pain is felt in the shin or the lower back even after sitting for a long time. In carrying this seat 2, it is light and convenient to carry, and the user can directly sit on the bag body 4 to feel convenience.