In the present research, amenity effect of ornamental foliage plants, imitation plants and photograph on human psychology were analyzed by means of electroencephalogram (EEG) and semantic differential technique. The experiments were carried out in a room in Ehime University in May of 2000. The following five objects with ornamental foliage plants, imitation plants or photograph in the room were evaluated by seventeen students (nine males and eight females) . Electroencephalogram of each subject was measured in the room. 1) Without plants (Control) ; 2) photograph of six ornamental foliage plants of Epipremunum aureum (Photograph) ; 3) six ornamental foliage plants (Plant) ; 4) mixture of three ornamental foliage plants and three imitation plants (Mixture) ; 5) six imitation plants (Imitation) . Ratio of alpha wave to beta wave was calculated as an index expressing the degree of amenity. As for semantic differential technique, factor analysis was performed based on twenty-five SD scales. Higher ratio of alpha wave to beta wave was observed in “Plant” for male subjects, indicating the amenity effect of ornamental foliage plants on human psychology. Three factors were extracted by the factor analysis. The first factor was concerned with comfortable psychology and the second factor was concerned with space arround the subject. The first factor score of “Plant” was higher than those of the other objects in female subjects but not in male subjects. The second factor score of “Photograph” was higher than that of “Mixture.” These results indicated the amenity effect on human psychology by plants.