1. A data classification supporting method for classifying unknown data, the method performed by a computer and comprising: displaying on a display a selection screen for selecting a classification map from a plurality of classification maps stored in a memory; wherein each of the classification maps comprises a plurality of classification areas, each of which comprises data sections; wherein each of the data sections comprises vector data decided based on prescribed learning data; wherein the classification areas respectively correspond to different diseases; and wherein the learning data comprise clinical data of patients judged by a doctor; receiving a selection of a classification map in the selection screen; reading the selected classification map from the memory; classifying the unknown data into a classification area of the plurality of classification areas based on the classification map read from the memory, wherein the unknown data comprises clinical laboratory data of a patient; comparing the vector data of each of the data sections with the unknown data; identifying a data section having the vector data closest to the unknown data as a target data section based on results of the comparing of the vector data and the unknown data; indicating a position of the target data section on the classification map; displaying the classification map, wherein the position of the target data section is indicated on the map; calculating a percentage representing a reliability of a result of the classifying of the unknown data, using the computer, wherein calculating the percentage comprises: calculating a first value based on either the unknown data or the vector data of the target data section and the learning data corresponding to each data section belonging to the classification area into which the unknown data is classified; calculating a second value by summating values calculated based on either the unknown data or the vector data of the target data section and the learning data corresponding to each data section belonging to any one of the plurality of classification areas with respect to all of the plurality of classification areas; and calculating the percentage by obtaining a ratio of the first value to the second value; and displaying the calculated percentage on the display.