A natural-language processing system includes a registration-candidate storage section that stores therein registration-candidate dictionary data, a judgment means that compares input data against the registration-candidate dictionary data to thereby judge whether or not the input data includes a word corresponding to the registration-candidate dictionary data, an inquiry means that inquires to a user whether or not corresponding dictionary data is to be registered in a dictionary storage section to accept a user's instruction if it is judged that a corresponding word exists, a dictionary registration means that registers the corresponding dictionary data in the dictionary storage section based on the input instruction, and a natural-language processing means that executes a natural-language processing onto the input data by using the dictionary data registered in the dictionary storage section.