The present invention provides an in-vehicle congestion-status display system that notifies railway users of a congestion status of each vehicle of a train. The in-vehicle congestion-status display system includes a main server that calculates a congestion rate immediately before boarding, which is a predicted value of a congestion rate when alighting of users is complete, of each vehicle of a train, based on a congestion rate during travel and an alighting rate acquired in a past and held as information indicating a difference between a congestion rate during travel immediately before arriving at the station and a congestion rate when alighting of users is complete after arriving at a next stop of the train, and a display device that notifies users of the congestion rate immediately before boarding calculated for each vehicle of the train.