14. The device of claim 10 , wherein the relation value calculator calculates a first sub-relation value between the first inquiry search word and the answer candidate keywords based on a frequency of the answer candidate keywords being included in the search word history, calculates a second sub-relation value between the first inquiry search word and the answer candidate keywords based on a frequency of the answer candidate keywords being included in the webpage information, and calculates the relation value through linear combination of the first sub-relation value and the second sub-relation value.
15. The device of claim 14 , wherein the relation value calculator calculates the first sub-relation value by further considering a distance value between the first inquiry search word and the answer candidate keywords in the search history.