PURPOSE: To measure chemical contamination of fresh air in an evaluation device of a semiconductor fabrication environment.

CONSTITUTION: An evaluating method of a semiconductor fabrication environment is characteristics in that fresh air introduced by a first fan 1 from the outside is removed in most part of dust involved therein by an air conditioner 2 and is blown off into an air supply chamber 11 by an air conditioner 8, and is thereafter fed into a clean room 13 after passage through a first glass filter 12 and then the air is again introduced into said air conditioner 8 and is circulated with disposition of a first evaluation semiconductor substrate 16 in the clean room 13, and in that in addition to a prior art where an environment evaluation in the clean room 13 is performed on the basis of the degree of contamination of the substrate 16 of the degree of chemical contamination of fresh air is measured on the basis of the degree of contamination of a second evaluation semiconductor substrate 22 placed in an evaluation air chamber 26 by directly feeding the air introduced by the first fan 1 into the evaluation air chamber 26 through a second filter 21.