1. A topic map based indexing apparatus, comprising: a Q/A pre-processing block for normalizing community Q/A lists in a single form, correcting grammatical errors, and removing insignificant symbols; a Q/A analysis block for analyzing the community Q/A lists to acquire Q/A analysis information; and a Q/A storage block for storing, in a community Q/A topic map, index information containing the community Q/A lists and the Q/A analysis information by removing redundant answers depending on the Q/A analysis information, removing insignificant answers based on the degree of reliability, ranking answer lists, extracting the highest ranking answer as a best answer, and determining a topic.