1. A person search method comprising: a first step of receiving face detection data including a feature extracted from a facial image detected from images of a plurality of cameras, an attribute of each camera and time information, and registering records including the face detection data in a first database or a second database depending on the attributes of the cameras; a second step of grouping records of a same person by searching for similar features in at least one of the first database and the second database using, as a search key, a feature of any record which is registered in the first database and has undetermined estimated person ID, assigning an estimated person ID to the record used as the search key based on a predetermined first rule, and updating a white list retaining the assigned estimated person ID in association with the feature thereof; a third step of detecting a suspicious person candidate by creating a suspicious person appearance list based on a predetermined second rule, and searching for similar features in the suspicious person appearance list using, as a search key, a feature of a record newly registered in at least the second database; and a fourth step of adding an appearance history to the record having the feature used as the search key in the third step when the suspicious person candidate is detected, and determining whether or not the suspicious person candidate corresponds to a suspicious person based on a predetermined third rule from the appearance history retained in the suspicious person appearance list.