Abstract: A bed in which a gap between back and leg side-rails is kept constant when a back bottom is raised. A first link and a second link (2, 3) are rotatably supported at lower ends thereof on a frame (1). A coupling (6) is fixed to the base end part of a deck (7), and upper ends of the first and second links (2, 3) are rotatably connected to the coupling (6). An L-shaped rotator (4) is rotatably supported by the frame (1), and one end of a third link (5) is rotatably connected to an upper end (1c) of the rotator (4). The other end of the third link (5) is rotatably connected to the coupling (6). An actuator (13) is supported by the frame (1), and a piston rod (13a) is rotatably connected to a central portion (1b) of the rotator (4). The rotator (4) is turned by an advancing of the piston rod (13a); the relative positions of the fourth, fifth, and sixth links are changed; and the leg side-rail slides along the frame (1).