The purpose of this study is to clarify the effect that the ceiling height difference of a room have on perception of room volume and spatial impressions. The various width and position of the ceiling height difference of a room is presented randomly. In the first experiment, The Method of Magnitude Estimation is used; subjects are then compared the volumes of high-ceilinged area and of low-ceilinged area. In the second experiment, subjects are then asked spatial impressions on 4 items (i.e. how many spaces are perceived, which space is felt as the main space, feeling of comfortableness, sense of oppression). Subjects are experienced the experimental room in standing and reclining postures. The results are summarized as below; 1). Perception of room volume and spatial impressions has highly correlated with the width and position of the ceiling height difference of a room. 2). Reclining postures were influenced by the ceiling height difference of a room more than standing postures.
