Abstract: Designs of thermo-hygrostat devices capable of uniformly maintain temperature and humidity inside a chamber are disclosed. One example of such a device can include, among others, a chamber in which a sample is accommodated and internal temperature and humidity can be controlled; a lower duct provided on a first side of the chamber and sending a fluid inside the chamber to an outside of the chamber; a temperature and humidity control portion provided on the lower duct and controlling temperature and humidity of a fluid received from the lower duct.