1. A predicted reference information generating method used when: processing a video image by dividing an image into areas; applying a temporal or spatial interframe prediction coding to each area of the divided image; and generating a predicted image of a processing target area based on a reference frame of the processing target area and reference information which is a vector and indicates a predicted target position of the processing target area in the reference frame, and generating predicted reference information as predicted information of the relevant reference information, the predicted reference information generating method comprising: a predicted reference information prediction data setting step of setting reference information, which was used when processing an area adjacent to the processing target area, as predicted reference information prediction data used for predicting reference information of the processing target area; a reference area reference information generating step of generating reference area reference information based on one or more pieces of reference information used when processing a reference area indicated by the predicted reference information prediction data, where the reference area reference information is the reference information used when processing the reference area; a predicted reference information prediction data updating step of updating the predicted reference information prediction data by using the generated reference area reference information; and a predicted reference information generating step of generating the predicted reference information by using one or more pieces of the updated predicted reference information prediction data, wherein: in the predicted reference information prediction data updating step, the predicted reference information prediction data is updated by changing the predicted reference information prediction data to the sum of the predicted reference information prediction data and the reference area reference information.