To solve problems of conventional seats, beds and the like that the tilt angle of a back seat is often adjusted by a reclining mechanism disposed in the back end of a seat cushion, however, when the back seat is reclined (rearward reclining), an upper body is relatively shifted to the cushion side relative to the back seat to cause back deviation, a support function of the backrest is insufficiently exerted and the clothes and the like are often rolled up.

With the rotation of a motor, screw rods start a rotary movement, and screw nuts provided at a bearing slidingly move on the screw rods. The back seat is connected to the bearing via pins, so that, when the pin is moved in a long hole simultaneously with the slide movement of the screw nut, the tilt angle of the back seat is changed. The back seat thus moves an interval S shown in Fig.2 in reclining so as to eliminate the back deviation.