Abstract: A problem is to carry out the removal of VOC and odor from VOC impregnated materials existing in a processed space without damaging interior materials and installed objects safely and with a low cost by controlling the humidity. The means comprise a humidification process wherein the inside of a processed space from which VOC should be eliminated is warmed to a high humidity within a range not being saturated, and hydrate complexes are formed between VOC absorbed/impregnated at impregnated materials and vapor-phase water molecules generated; and the second process wherein the VOC hydrate complexes formed inside VOC impregnated materials on said humidification process are radiated from the VOC impregnated materials into the processed space by lowing the humidity.