1. A transportation state notification method, comprising: detecting a plurality of types of events relating to lot transportation in a plurality of temporary storage devices which are provided at different locations, to which lots are transported, and in which the lots are stored; updating lot state data including data indicating an event transition of each of the lots based on the detected events; determining whether the lots are in an under transportation state or an awaiting transportation state based on the data indicating the event transition, and displaying an image showing a state of a target lot at a predetermined time as an image showing a transportation load state; calculating a transportation load index based on a ratio of a total number of the lots to a number of lots in the under transportation state; and displaying an image showing the transportation load index as the image showing the transportation load state.