Proposed are a data-organization support method for efficient user-initiative on-screen data classification and a program product for achieving the data-organization support method. A data file, a correction of items to be classified is loaded to display a classification window having a group window and several item (contents-view) windows. An on-screen operation, such as, shifting an item over the item windows initiates item processing such as change in a group to which the item belong. An on-screen operation, such as, shifting a group in the group window initiates group processing such as displaying the contents of the group or change in group hierarchy. The results of classification are reflected on the group window and stored as a classification history.