A data management method including accepting a request of polygon data including data pertaining to latitude/longitude of each vertex of a polygon, specifying a minimum unit rectangle matching a minimum bounding rectangle of the polygon or including the minimum bounding rectangle from plural unit rectangles formed by recursively dividing a two-dimensional space including a latitude/longitude range and being equally divided in X and Y directions in the same number, generating a character string by assigning values to the minimum unit rectangle or all unit rectangles including the minimum unit rectangle in correspondence with the number of divided parts of the two-dimensional space in the X and Y directions, and alternately arranging the values, in the X or Y direction, starting from values corresponding to a large unit rectangle among the unit rectangles, and storing the polygon data in correspondence with a key including the character string.