1. A structural element detecting apparatus for detecting predetermined structural elements included in predetermined subjects from within images that include the subjects, comprising: a structural element candidate detecting section, for detecting structural element candidates by discriminating characteristics inherent to the predetermined structural elements, from among characteristics of the images; a subject detecting section, for detecting subjects that include the structural element candidates by discriminating characteristics inherent to the predetermined subjects, from among characteristics of the images in the vicinities of the structural element candidates; and a structural element confirming section, for confirming that the structural element candidates are the predetermined structural elements, by discriminating characteristics inherent to the predetermined structural elements with a higher degree of accuracy than that of the structural element candidate detecting section, from among the characteristics of the images in the vicinities of the structural element candidates, which are included within subjects detected by the subject detecting section; wherein the structural element confirming section performs discrimination, utilizing data regarding subjects detected by the subject detecting section; wherein the structural element confirming section compares the number of structural element candidates, detected by a first structural element candidate detecting process and confirmed as being the predetermined structural elements, against the maximum number of structural elements which are possibly included within the subjects detected by the subject detecting section; and a second structural element candidate detecting process, having a higher detection rate than the first structural element candidate detecting process, is executed in the case that number of structural element candidates, which have been detected by the first structural element candidate detecting process and confirmed to be structural elements by the structural element confirming section, is less than the maximum number.