1. A semantic-based search system comprising: a log generating unit configured to generate a common log storing knowledge corresponding to general knowledge and a user log stored by reflecting user preference; an instance analyzing unit configured to analyze vector characteristics corresponding to an instance among interpretation alternatives according to a keyword input by a user; a weighted value calculating unit configured to calculate weighted values of confidence values and cosine similarity values of interpretation alternatives including vector characteristics of the instance with respect to at least an one of the common log and the user log; and an aligning unit configured to align rankings of the interpretation alternatives according to the keyword input on the basis of the calculated weight values of the confidence values and the cosine similarity values.