1. An information classification system that classifies information by assigning a classification identification value to the information, comprising: a knowledge base that receives classification information to be classified as a word string, conducts language analysis of the classification information to acquire a plurality of keywords that the classification information includes and classify the plurality of keywords into elements made up of a classification target word and a related word that modifies the classification target word, and conducts a search with the related word being for a judgment condition for decision of the classification while separating the classification target word from the related word, so as to assign the classification identification value to the information; a classification candidate extraction section that extracts the classification identification value that the knowledge base assigns to generate an automatic classification result; and a classification update section that receives the automatic classification result, displays a GUI for classification confirmation allowing confirmation of correctness of the automatic classification result, and corrects registered items in the knowledge base with a correction value received through the GUI for classification confirmation while referring to log data that is a processing history about automatic classification for the language analysis and the element classification.