An negative example prediction processing method for predicting a likelihood of examples being negative for data where, with respect to a certain problem, it is not known whether the data is for a correctly worded positive example or for an incorrectly worded negative example. In this negative example prediction processing method, an unknown example x is inputted and a determination is made as to whether or not the example x exists in a positive example database provided in advance. If the example x does not exist, a typical probability of appearance p(x) for the example x is calculated, and a likelihood Q (x) of the example x being an negative example is calculated from the probability of appearance p(x).