Disclosed are a method and apparatus for building information on an emotion lexicon. The method according to the disclosure may include: retrieving specific documents on the basis of a specific emotion expression lexeme to derive emotion basis lexemes of the emotion expression lexeme from sentences including the emotion expression lexeme; and deriving a new emotion basis lexeme determined among the derived emotion basis lexemes according to at least one predefined new lexeme criterion and then storing the new emotion basis lexeme in an emotion lexicon. The method may include writing emotion expression lexemes associated to the emotion basis lexemes and assigning an emotion strength to them by multiplying an emotion strength value associated with an emotion expression lexeme and a sum of weights associated with a plurality of modifiers of emotion expression lexemes.