A bed device includes a bed frame, a bed plate body, a back-up mechanism, an actuating shaft, a mounting member, a transmission member, and a pressing member. The bed plate body includes: a fixed bed portion； and a back bed portion, having: a central back portion and a pair of side back portions that are rotatably connected to both sides of the central back portion in a forward direction, and are configured to be rotatable relative to the fixed bed portion . The back-lifting mechanism lifts the back-bed portion of the bed plate body. The actuation shaft is rotatably supported by the back of the central back. The mounting member is provided in the middle of the actuating shaft. The transmission member is fixed at one end to the mounting member, and the other end is fixed to a portion where tension is generated when the back lift mechanism is driven to drive the back bed portion in the standing direction, and the actuation shaft is rotated in a predetermined direction by the tension. The pushing member can be arranged at both ends of the actuating shaft at a variable angle, and when the back bed portion is rotated by the transmission member, the pair of side backs can be positioned at the actuating position of rotating forward, and not Either of the non-actuated positions rotating forward.一種床裝置，具備：床框架、床板體、抬背機構、作動軸、安裝構件、傳動構件及推壓構件。床板體具備：固定床部；及背床部，具有：中央背部及朝前方向旋動地連結於該中央背部之兩側的一對側部背部，且設置成可相對於固定床部旋動。抬背機構使床板體的背床部升降。作動軸可旋轉地由中央背部的背面所支撐。安裝構件設置於作動軸的中間部。傳動構件是一端固定於安裝構件，並且他端固定於使抬背機構作動而將背床部朝立起方向驅動時會產生張力的部分，且藉由張力使作動軸朝預定方向旋動。推壓構件可變更角度地設置於作動軸的兩端部，且在背床部藉由傳動構件旋動時，可使一對側部背部定位於往前方旋動的作動位置、與不往前方旋動的非作動位置之任一者。
