Hader and Park (1978) introduced the idea of slope rotatability, and Park (1987) introduced the concept of slope rotatability over all directions, and gave necessary and sufficient conditions. Park and Kim (1992) proposed a measure that represent the extent of slope rotatability for a given response surface design. Kim (1993) proposed a measure that represent the extent of slope rotatavility over all directions. In this paper, we embodied the measure of slope rotatability over all directions. Examples of applying this measure to some response surface designs are also given. In this response surface design of slope rotatavility over all directions, we obtain the mean slope variances on the spherical surface to select better experimental design varying the number of center points and radius.