PURPOSE: To simplify the number of testing times and to also shorten a testing time by enabling the assembling a humidification test system into a test pattern, by providing the humidification testing system for supplying humidity conditioned gas prepared by mixing heating gas, cooling gas and steam other than a rapid heating and cooling testing system.

CONSTITUTION: Gas to be mixed in the downstream side of a heating apparatus 16 and a cooling apparatus 27 is converted to the medium temp. gas by both of said cooling apparatus 27 and the heating apparatus 16 and the medium temp. gas is sent into a specimen chamber 3 through a siroco fan 20. Furthermore, because the medium temp. gas flowed into the specimen chamber 3 while converted to the humidity conditioned gas containing steam, a medium temp. humidifying test is applied to a specimen. When the humidity in the medium temp. gas is increased at a certain ratio, the operated cooling apparatus 27a is stopped and, to the contrary, stopped cooling apparatuses 27b, 27c are operated. Because the cooling apparatus 27c is inferior to cooling capacity but rich in dehumidification capacity and a punched plate 28 for suppressing the flowing speed of the medium temp. gas is further provided, moisture is effectively removed from the humidity conditioned gas flowed into an auxiliary cooling chamber 23 and discharged from a drain hole 29.