Similar document retrieving method and system for retrieving similar documents from a document database storing plural documents written in different languages with high accuracy while suppressing retrieval noise even when difference is found in the number of registered documents in dependence on the species of description languages. Statistical information concerning the registration-subjected documents is collected on a language-by-language basis upon registration thereof. Upon retrieval of documents similar to a query document, weights of words extracted from the query document are taken into account and on a language-by-language basis by referencing the statistical information.