PROBLEM TO BE SOLVED: To store fruit vegetables for a long period by controlling atmosphere in a storage chamber. SOLUTION: In environmental control of oxygen, etc., necessary to retain freshness of an agricultural product of a storage chamber (1), adsorbing agents (11a and 11b) packed with a nitrogen adsorbing agent are used and a gas in the chamber is introduced into the adsorbing agent under conditions having high oxygen concentration in the chamber to adsorb nitrogen and slightly adsorbable oxygen is released to the outside of the system in an adsorbing process. Then, the adsorbed nitrogen is led to reduced pressure condition to recover the nitrogen and adsorption of CO2 is carried out for a longer adsorption time than nitrogen adsorption under conditions having high CO2 concentration of the chamber and the CO2 is led to reduced pressure condition and released to the outside of the system and adsorption of a volatile organic substance is carried out in an adsorption time equivalent to that of CO2 adsorption and the adsorbed volatile organic substance is led to the reduced pressure condition and released to the outside of the system. The removal of oxygen, CO2 volatile organic substance to the outside of the system is carried out by changing adsorption time by one kind of adsorption tower. In this case, a blower circulating the gas in the system and a vacuum pump for making reduced pressure conditions is covered with atmospheric gas in the chamber.