PURPOSE: To reduce the amount of frost sticking on a cooler, etc., arranged in a precooling chamber by supplying dry air which is obtained by reducing the moisture of outside air by a dehumidifier to a test chamber through the opening operation of an opening/closing valve which is associated with a room-temperature damper when the outside air is introduced to the test chamber through the opening operation of the room-temperature damper.
CONSTITUTION: An outside air intake port 2 and a discharge port 3 which are linked with the outside air are provided to the test chamber 1 of the thermal shock testing device and those intake port 2 and discharge port 3 are opened and closed by the room-temperature damper 4. This chamber is provided with a preheating chamber 9 where a heater 6 and a fan 7 are arranged and the precooling chamber 14 where a cooler 11 connected to a refrigerator 10 and a fan 12 are arranged adjacently across a heat insulating partition wall 5. Further, an opening part 15 which links the chamber 1 and preheating chamber 9 with each other is opened and closed by a high-temperature damper 16 and an opening part 17 which links the chamber 1 and precooling chamber 14 is opened and closed by a low-pressure damper 18. Further, the dehumidifier 21 composed of a cooler 19 connected to the refrigerator 10 and a reheater 20 is arranged on the outside intake side of the intake port 2 and the opening/ closing valve 22 which is opened and closed according to the operation of the damper 4 is arranged in the connecting circuit for the refrigerator 10.