The utility model relates to a window opening device, which belongs to the technical field of construction hardware, and comprises a motor arranged in a case, a transmission gear, a chain wheel and a chain, wherein both the two ends of the case are provided with a connecting port, and the motor is connected with the external connecting wire through the connecting port. The utility model not only saves more external connecting wires, facilitates on-site installation, and can make more window opening devices synchronously work without specially arranging the external centralized control box, thereby saving cost.