Why would a lecturer flirt with a student and when she tries to talk to him or call?

him on the behaviour (not to sue him or anything) he denies, denies, denies? He has done such things as oggling her bosom from the side as she leaves his office, come very close to her face doing the triangular eye to eye and down to the mouth when they were looking in a book together, if she wears a skirt he glances down at her knees, when she leaves he checks out her bottom, he stares at her lips when she is speaking, his conversation can have innuendo in it, if she slips on a chair or fixes herself on a chair he will try and get a glance at the shape and everything of her decolletage. He can also stare at other womens' bottoms in the clroom environment. All of these incidents have certainly not been fabrications or chimeras on the girls part but he denies it when confronted??