Support device, adjustable by electric motor, for supporting cushioning of a piece of furniture for sitting or lying on, in particular a bed mattress, has base body with first adjustable support part, in particular pivotable, relative to second support part. Electric motor adjusting device adjusts first support part, and has first and second adjusting unit provided on opposite longitudinal sides of base body. Rotationally supported component of first adjusting unit is connected, rotationally fixed, to similar component of second adjusting unit by a connecting shaft, and axial ends of connecting shaft engage in recesses in rotatably supported components. Connecting shaft is axially movable between a first position in which rotatably supported components are connected rotationally fixedly by connecting shaft, and a second position in which one end of the connecting shaft is released from recess, and connecting shaft is pretensioned in first position by a spring.
