A client device accepts event information for which a people flow prediction is to be performed from a user and the client device inputs the accepted event information to a people flow prediction device. The people flow prediction device outputs a result of people flow prediction responsive to the input event information to the client device and the client device displays the result of people flow prediction to the user. The people flow prediction device performs a people flow prediction by temporally and spatially allocating an event attendance which has been input from the client device to pathways, each connecting a transport facility at which a people flow originates and an event site. Consequently, it is possible to predict a flow of people who attend an event or the like, the people flow differing from that in an ordinary situation, without need to input real-time data.