The purpose of this study is construction of the evaluation method for easily moving up and down steps in consideration of the interaction of the visual factors, the size of steps and the human characters such as age, height, and foot length. This paper shows the interaction of the visual factors and the size of steps in steady adaptation state, by 14 young girls who are regarded as a same human character. Experimental variables were luminance contrast, illuminance, rise, and tread. The number of steps were 4-5. The interior of laboratory and the surface of steps were matte and white, then the visual field luminance was almost uniform. As the result, it was able to be confirmed that the gradual evaluation structure (Physical value → Physical evaluation → Quality evaluation → the ease of moving up and down steps) is applicable to the evaluation for easily moving up and down steps. In this experimental condition, the effect of visual factors on the ease of moving up and down steps are smaller than the size of steps effect.
