To realize a precise language cross document retrieval by realizing a retrieval request translation having preciseness and soundness in a language cross information retrieval system for realizing a retrieval when the languages of a retrieval request and a document to be retrieved are mutually differed.

A mechanical translation part 15 mechanically translates the retrieval request inputted through an input part 11 to the same language as the document to be retrieved. A phonetic character conversion part 16 converts a phonetic character the mechanical translation part 15 fails to translate in the retrieval request to a phonetic character of the same language as the document to be retrieved. A retrieval part 14 retrieves a document including the retrieval word from a document database 18 based on the retrieval word generated by the mechanical translation part 15 and the retrieval word provided by the phonetic character conversion part 16.