Abstract: A bed device comprises a bottom unit including a back bottom, a hip bottom, and a leg bottom connected to one another, and a drive mechanism capable of changing a posture of the bottom unit from a supine posture in which the back bottom, the hip bottom, and the leg bottom are aligned horizontally to a back lifting posture and a sitting posture. The drive mechanism allows the back bottom to stand up about the hip bottom in the change from the supine posture to the back lifting posture, and rotates the leg bottom around one end of the hip bottom and accommodates the leg bottom on a back side of the hip bottom in the change from the back lifting posture to the sitting posture.