Abstract: Division plates inside a constant-temperature box form an inner box for positioning an electronic device to be tested. Airflow guiding devices, temperature regulators, and airflow regulators are positioned inside the constant-temperature box. The airflow guiding devices direct air from air vents near the bottom of the constant-temperature box into the inner box. The temperature regulators adjust air temperature between the inner box and the constant-temperature box. The airflow regulators regulate air directed by the airflow guiding devices so as to stabilize the speed of airflow inside the inner box. Therefore, when the electronic device is tested, the test result will not be influenced by airflow.