Abstract: A piece of furniture convertible from a seat into a bed and having a seat portion and an adjoining back portion which is connected thereto by a hinge for enabling the seat portion and the back portion to rotate with respect to one another between an automatically stabilized seat position of the piece of furniture, wherein the angle between both portions is minimal, and a flat position of the piece of furniture, wherein the angle between both portions is maximal. Further there are provided legs for supporting the seat portion in the seat position and the seat portion and the back portion in the flat position of the piece of furniture. Located between the seat portion and the back portion is a locking device for locking the seat portion and the back portion with respect to one another in the seat position.