How does a person's personal space change when the person approaches or retreats from another person? In this study, we examine the anisotropy of personal space in a virtual room constructed by three-dimensional computer graphics. In two experiments, a participant took the first-person point of view, and an unfamiliar avatar was placed in the virtual room. The stop-distance technique was used to measure the personal space between the participant and avatar. The participant was required to approach the avatar until he or she felt uncomfortable (approaching condition) or to retreat from it until he or she felt comfortable (retreating condition). We also controlled the room size and the unfamiliar avatar's direction. The results clearly showed that the personal space was larger under the approaching condition than under the retreating condition. Moreover, we found that the avatar's direction influenced the effect of the room size on personal space.