The invention relates to an electric mechanical extension device for a movable sofa. The electric mechanical extension device is mainly suitable for movable sofas, particularly electric rocking chairs and swinging chairs. The electric mechanical extension device for the movable sofa comprises a mechanical extension device and an electric device, wherein the electric device consists of a motor, a front motor connecting pipe, a back motor connecting pipe, a motor head mounting piece, a motor motion slide block, a slide block mounting piece, a rotating connecting piece and a rotating bent piece; the front motor connecting pipe is connected with a leg connecting piece; the motor head mounting piece is connected with the front motor connecting pipe, and is rotationally connected with the motor; the motor motion slide block is arranged on a motor slide rail; the sliding mounting piece is fixed on the back motor connecting pipe, and is rotationally connected with the motor motion slide block; the back motor connecting pipe is connected with the rotating bent piece; the rotating bent piece is rotationally connected with an ascending connecting piece; the rotating connecting piece is rotationally connected with the rotating bent piece and a mounting plate. The electric mechanical extension device is simple in structure, safe and reliable for driving, high in efficiency, low in cost and high in comfort.