A translation direction specifying unit specifies a first language and a second language. A speech recognizing unit recognizes a speech signal of the first language and outputs a first language character string. A first translating unit translates the first language character string into a second language character string that will be displayed on a display device. A keyword extracting unit extracts a keyword for a document retrieval from the first language character string or the second language character string, with which a document retrieving unit performs a document retrieval. A second translating unit translates a retrieved document into its opponent language, which will be displayed on the display device.