To surely take a lying posture for not adversely affecting the lumbar vertebra by tilting a pad seat to a horizontal floor seat so as to make the axis of a human body in the posture of lying on his/her back be almost straight.

For a bed A, the floor seat 2 is installed to a base frame 1 so as to make the upper surface horizontal and a mattress 3 housing cushions provided with appropriate hardness is mounted on the floor seat 2. In order to bend the upper surface of the flat floor seat 2 of the general. purpose bed, the pad seat 4 is formed in a triangle side face shape by using the rigid material of wood or synthetic resin or the like and is placed on the upper half body side of the floor seat 2 so as to position a high part to a head side. In such a manner, when a person lies on his/her back on the upper surface of the pad seat 4 and the floor seat 2, the axis P of the human body in the posture becomes almost straight. Thus, since the force of bending the lumbar vertebra hardly acts in the state of lying on the back, even the person with lumbago can comfortably and quietly sleep without being distressed by a pain.