PURPOSE: To remove ethylene in a vegetable preservation container and enable preservation of vegetables for a long period by producing a pressure difference between both surfaces of specific gas separation membranes and admitting air enriched with carbon dioxide and steam into the vegetable preservation container.

CONSTITUTION: A preservation house, composed of membrane modules 12 composed of gas separation membranes (12a) having a high permeability to gaseous carbon dioxide and steam and low permeability to ethylene and a suction blower 13 for sucking air in a vegetable preservation container 11 connected to the membrane modules at two places and provided with the aforementioned suction blower on the discharge side of the above-mentioned membrane modules so that the space on the discharge side and the space on the suction side may be divided into sections and prevented from their being connected. A pressure difference is produced between both surfaces of the gas separation membranes to increase the gas permeation flow rates of the gaseous carbon dioxide and steam and admit air enriched with the gaseous carbon dioxide and steam into a preservation container. Air freed of ethylene is provided in the interior of the container to enable preservation for a long period.