To have solidity and a soft touch in collision and violent contact, to reduce pain of an infant, and to exchange or clean a buffer sheet when broken or stained by detachably attaching the buffer sheet at least inside a rigid circle body and constituting an infant circle of them.

A plurality of circle segments 10... formed of steel round rods, practically round pipes, are connected to be formed into a rigid circle body and each circle segment 10 is bent into a U shape to be formed into the round rod top end and both ends. A bag-shaped buffer sheet 2 is covered over the each circle segment 10 constituting the rigid circle body. One buffer sheet 2 may be detachably attached to the inside of the rigid circle body, at least attached to the inside of the rigid circle body, however, preferably covers the each segment into a bag shape. This constitution can extremely easily and quickly cover all the circle segments 10 except for the bottom side of the round rods 10b, 10b.