A classification apparatus (1) is a classification apparatus that classifies sequential data, in which input communication destinations in a plurality of communications are recorded in order of occurrence of the communications, into a class that has a similar feature, and includes a numerical vector calculation unit (14) configured to calculate numerical vectors that represent characteristics of communication destinations for each of the communication destinations, on the basis of sequential data in which the communication destinations in a plurality of communications are recorded in order of occurrence of the communications, and a classification unit (15) configured to classify the sequential data into a class that has a similar feature, on the basis of order relation of the communication destinations of the numerical vectors.