An information classifying device calculates, for a plurality of populations containing pieces of sample information, evaluation distance between a center of gravity of the pieces of sample information belonging to each population and a piece of sample information as an object of classification (object sample), calculates statistical information such as mean, variance and standard deviation of the evaluation distance for each population, evaluates the evaluation distance of the sample information to the population based on the evaluation distance and the statistical information and evaluates degree of assignment relevancy of the object sample to the population, determines to which population the object sample is to be assigned in accordance with the degree of assignment relevancy, and assigns the object sample to the population. Evaluation distance between the center of gravity of each updated population and the object sample belonging to each population is calculated. If the degree of assignment relevancy to every population is out of a prescribed range, a new population is formed, and the object sample is assigned to the new population. Thus, autonomous and stable classification of object sample to a population becomes possible.