1. A person retrieval apparatus for retrieving a person on the basis of personal biometric information, comprising: an extraction section which extracts personal biometric information from an image taken by a camera; a quality determination section which determines a quality of the biometric information extracted by the extraction section; a setting section which sets a reliability level of the biometric information extracted by the extraction section on the basis of the quality determined by the quality determination section; a memory which stores the biometric information extracted by the extraction section and the reliability level set by the setting section in association with each other; and a retrieval section which performs person retrieval processing on each piece of biometric information stored in the memory, in descending order of the reliability level corresponding to each piece of biometric information.