A person detector detects a person in an area facing one door surface. An open/close detector detects whether the door is in an open or closed state. When a detected state of the door switches from a closed state to an open state, an open-state person detection information recorder records whether the person detector is detecting a person or not. When the state of the door detected by the open and close detection sensor switches from the open state to the closed state, a closed-state person detection information recorder records whether the person detector is detecting a person or not. A room entry and exit detector detects that there occurs an entry into the room and there occurs an exit out of the room on the basis of a content recorded by the open-state person detection information recorder and the closed-state person detection information recorder.