A support device adjustable with an electric motor for supporting the upholstery of a piece of seating and/or reclining furniture, in particular a mattress of a bed, with a base part , with a support part , which is connected to the base part so as to be pivotable about a first pivot axis , and with an electromotive drive device , which is in operative connection with the base part and the support part for pivoting adjustment of the support part relative to the base part , wherein the base part and the support part are configured and operatively connected to the drive device in such a way that the support part can be adjusted between an unadjusted starting position, in which the support part rests flat on the base part , and an end position of the adjustment movement, in which the support part is arranged at an angle to the base part , characterized in that the electromotive drive device has a spindle drive which has a stationary, rotatably mounted threaded spindle which is in rotary drive connection with an electric motor of the drive device and on which is arranged a spindle nut which is movable in the axial direction of the threaded spindle and forms the output member of the electromotive drive device , in that at least one first wedge-like lifting guide element is arranged on the base part in the region of the first pivot axis and at least one second wedge-like lifting guide element is arranged on the support part opposite the first wedge-like lifting guide element , and in that the lifting guide elements are arranged in the path of movement of a free end of a plunger , the other end of which is connected to the spindle nut in an articulated manner and pivotably about a second pivot axis parallel to the first pivot axis in such a way that the free end of the plunger presses against the lifting guide elements in order to pivot the support part relative to the base part . with a base part , with a support part , which is connected to the base part so as to be pivotable about a first pivot axis , and with an electromotive drive device , which is in operative connection with the base part and the support part for pivoting adjustment of the support part relative to the base part , wherein the base part and the support part are configured and operatively connected to the drive device in such a way that the support part can be adjusted between an unadjusted starting position, in which the support part rests flat on the base part , and an end position of the adjustment movement, in which the support part is arranged at an angle to the base part , characterized in that the electromotive drive device has a spindle drive which has a stationary, rotatably mounted threaded spindle which is in rotary drive connection with an electric motor of the drive device and on which is arranged a spindle nut which is movable in the axial direction of the threaded spindle and forms the output member of the electromotive drive device , in that at least one first wedge-like lifting guide element is arranged on the base part in the region of the first pivot axis and at least one second wedge-like lifting guide element is arranged on the support part opposite the first wedge-like lifting guide element , and in that the lifting guide elements are arranged in the path of movement of a free end of a plunger , the other end of which is connected to the spindle nut in an articulated manner and pivotably about a second pivot axis parallel to the first pivot axis in such a way that the free end of the plunger presses against the lifting guide elements in order to pivot the support part relative to the base part . <EOS>