A sleep sofa includes a main frame, a seat unit, a back unit and a supporting linkage assembly that can move the back unit along an arc to the front of the seat unit when the sleep sofa is converted to a bed state, the supporting linkage simultaneously lifting the rear side of the seat unit, which is mounted in the main frame to slope downwardly from horizontal at about a 5° angle, up to horizontal. Once positioned in front of the seat unit, the back unit can be pushed downwardly so as to rotate into a locked parallel orientation with the seat unit. The seat cushion of the seat unit and the back cushion of the back unit form the bedding surface. Pushing a back release tube will unlock the back unit to allow it to be returned to a sitting positioning above the seat unit (tilted rearwardly to define an angle of about 115° with the seat unit). During its arc movement over the seat unit, the back unit will rotate around pivots on the side backs thereof.