Human-friendly robot which supports and assists human being directly beside human being is expected as it has become an aging and decrease-in-the-birthrate society. In addition to the safety function to avoid dangers for human being, we think the informational affinity function is important such as to announce surrounding people the robot's following motion before beginning to move. A person can anticipate and guess other's motion considering human body's functional features and behavioral pattern as common sense. This paper discusses the preliminary-announcement and display function of mobile robot's following motion, the direction of motion and the speed of motion, by using a omni-directional display, magic ball (R). This examines the four types of eyeball expression, one-eyeball type, two-eyeball type, will-o'-the wipe type, and armor-helmet type.