The invention discloses a body weight self-balancing chair / bed, which mainly comprises a bed frame, an upper body frame, a lower body frame, a bed surface, thigh balancing rods, a connecting rod, a self-balancing adjusting rod and a limiter, wherein a supporting leg is arranged at each of four corners of the bed frame, so that a C-shaped structure is formed; and the upper body frame, the thigh balancing rods and the lower body frame are sequentially connected, so that a three-sectional structure is formed, and through mechanical linkage, one plane and three fold surfaces are formed. According to the body weight self-balancing chair / bed provided by the invention, an existing normal bed surface is designed as a three-sectional structure, wherein the upper body section can be turned upwards and serve as a backrest, the middle section is in charge of bearing weight from hips to knees, meanwhile, the middle section functions as an action force source for turning up the upper body section, and the lower body section is synchronously turned downwards when the upper body section is turned upwards and is in charge of supporting leg space below the knees and feet, so that the body weight self-balancing chair / bed can be optionally switched between a standard lying bed and a standard chair; strong impact and vibration can be avoided when a person having difficulty in moving gets on or gets out of the bed; in addition, the body weight self-balancing chair / bed, which conforms to ergonomic under a mediate state, can offer an optimum resting position, so as to relieve body fatigue; and an entire gesture transformation process is completely adjusted on the basis of body self-weight balance, without the assistance of external force.