PURPOSE: To control the environment in the chamber of a thermo-hygrostatic apparatus suitable for the cultivation of viruses and bacteria, by placing a box made of a highly heat-conductive material in the chamber to prevent the flow of air between the chamber and the box, and placing an illumination device to illuminate inside of the box from its outside.

CONSTITUTION: The titled apparatus is composed of the chamber 7 containing the heating means 11, the cooling means 12, the means 13 for the circulation of air in the chamber, and the means 27 for illuminating inside of the chamber, and the inside of the chamber is controlled at specific temperature, humidity, illumination, etc. free from temperature gradient. The box 20 is placed in the chamber 7. The opening of the box 20 is closed with the door 22 to inhibit the flow of air between the chamber and the box. The illumination device 27 to illuminate in the box 20 is attached outside of the box, and the walls 20a, 20b, etc. are constructed with a highly-conductive material. The space in the box 20 can be controlled at constant temperature and humidity, the temperature gradient and circulation of air flow in the box can be minimized, and the environment can be made suitable for the cultivation of viruses and bacteria.