Reaction time as a function of rotation angle in spatial perspective-taking was investigated with an original perspective-taking task. Relation between reaction time and rotation angle was assumed to indicate characteristics of image used in the perspective-taking processing. Mean reaction time of 192 values from twelve students participating in the first experiment was calculated. The regression line formed a mountain shape which peek was on the opposite of subject position, Three female students were requested to join again to the second experiment. Mean reaction time of 288 values was calculated individually . The regression lines demonstrated peculiar patterns and one of them had its peek on 135 degree definitely. These findings indicated that image was mentally rotated continuously and the mental operation was different in homogeneity of rotation speed among individuals.