1. A face recognition apparatus that recognizes faces of a plurality of persons, comprising: a plurality of cameras configured to pick up, in time series, the plurality of persons moving at the same time in the same place; a face image acquiring unit configured to acquire respective face image sets including face images in time series from the respective image sequences; an intra-sequence classifying unit configured to add the face images in the respective face image sets into fragmental face image sets each including the face images having high correlation with each other by (1) obtaining simple similarities between the acquired face images and latest face images which belong to the fragmental face image sets respectively, (2) obtaining a difference between a time when the acquired face images are acquired and a time when the latest face images of the fragmental face image sets are acquired, (3) obtaining first similarities by dividing the simple similarities by the difference for each of the fragmental face image sets respectively, and (4) adding the acquired face images into the fragmental face image set having the first similarity highest among the respective first similarities; an inter-sequence classifying unit configured to generate integrated sets each including the fragmental face image sets having high correlation with each other by (1) obtaining second similarities between the fragmental face image sets respectively, and (2) integrating the fragmental face image sets having the second similarities high with each other; a reference image storing unit configured to store respective reference face image sets of respective persons acquired in advance for identification; and an identification unit configured to compare the respective integrated sets with the reference face image sets to identify the persons.