1. An information updating device for updating target object map information for displaying detail information about details of a plurality of target objects located in a predetermined position such that the detail information corresponds to a positional relationship of the plurality of the target objects, the device comprising: a new detail information acquirer for acquiring the detail information about the new target object; a new target object position recognizer for recognizing a position where the new target object exists; a target object map information acquirer for acquiring the target object map information; an existing detail position recognizer for recognizing, based on the target object map information acquired by the target object map information acquirer, a display position for detail information of an existing target object that is different from the new target object, the detail information of the existing target object possibly visually interfering with the detail information of the new target object; a detail position setting section for setting a display position for the detail information of the new target object at a position corresponding to the position of the new target object but not overlapping with the detail information of the existing target object; and an update processor for updating the target object map information such that the detail information of the new target object is displayed at the display position that is set by the detail position setting section.