A double-layer cord rolling device includes a driving unit, and a cord rolling unit disposed under the driving unit. The driving unit has an upper base, two torsion spring gears rotatably disposed in the upper base and engaged with each other, and a torsion spring connecting the two torsion spring gears. The cord rolling unit has a lower base connected with the upper base, two cord rolling wheels disposed in the lower base in a way that they are capable of rotating synchronously and coaxial with the torsion spring gears respectively, and two lift transmission cords connected to the two cord rolling wheels respectively. A transmission shaft is employed to connect a torsion spring gear and a corresponding one of the cord rolling wheels, enabling them to rotate synchronously.