1. A voice recognition system for recognizing input voice information pronounced by a user and comprising: a recognition dictionary for storing voice information; a primary voice recognition unit which performs primary voice recognition of the input voice information by the use of said recognition dictionary to produce a primary voice recognition result which is specified by a voice feature of the input voice information; a recognition result judgment unit which judges whether the primary voice recognition result is to be accepted or rejected; a transceiver unit which sends the voice feature to additional voice recognition means for performing secondary voice recognition, when the primary voice recognition result specified by the voice feature is rejected by said recognition result judgment unit and for receiving a secondary voice recognition result produced by the additional voice recognition means; a recognition result output unit which outputs the primary voice recognition result specified by the voice feature and outputted from said recognition result judgment unit or the secondary voice recognition result received by said transceiver unit to an exterior of said voice recognition system; a settled result input unit which receives settlement information on the primary voice recognition result or the secondary voice recognition result outputted to the exterior of said voice recognition system; and a dictionary content control unit which updates said recognition dictionary based on the settlement information inputted by said settled result input unit; wherein: said dictionary content control unit has a word history list which includes an order of use of each word and a frequency of use of each word and deletes, from the recognition dictionary, a word based on at least one of the oldest word and the smallest word of the frequency included in the word history list when an amount of the words in said recognition dictionary exceeds a processing capability of said voice recognition system.