1. A person search method comprising the steps of: creating a database by detecting facial images in input images, extracting features from the facial images, and registering the features in the database together with time information; specifying facial images which are detected automatically or specified manually from the input images as facial images to be determined; searching the database created in the creating step for similar faces for limited time on a time axis; calculating the number of cases with higher similarity than a predetermined value among search results of the searching step, and determining that the number of appearances is large and a possibility of a prowling person is high if the number of cases is large, and that the number of appearances is small and a possibility of prowling person is low if the number of cases is small; and calculating similarity between a facial image of a pre-registered non-suspicious person and a facial image of a person whose appearance number is large, and re-determining that the person is not a suspicious person if the similarity is high, regardless of determination of the determining step.