Information regarding an obstacle region and information regarding an empty region are optimally updated to minimize an information amount. In the obstacle region, an obstacle exists in space where a mobile body moves. In the empty region, an obstacle does not exist. According to the disclosure, there is provided an environmental information update apparatus including an update unit that updates information regarding an obstacle region and information regarding an empty region, an obstacle existing in space where a mobile body moves in the obstacle region, the obstacle not existing in the empty region, in which the update unit updates the obstacle region, and updates the empty region on the basis of different periods of elapsed time.