Is he re-presenting your whole presentation, and nothing else, or has he just taken a few results slides and included them in his presentation along with some other stuff?
If the latter, this is completely normal. You should be acknowledged during his presentation of course, and hopefully he will do this as he presents the work, or at least at the end. The only way most group leaders do research is by supervising the people who *actually* do the research, so of course they present their students and postdocs work at conferences, often they can bring themes from different people's projects together, to give some additional insights, for example. It is a very good sign if your supervisor wants to talk about your work, and it should give you and your work greater exposure to a wider audience. Some supervisors will use whole slides the way you made them, others might just use the images and put new text, etc.
If he is just re-presenting your whole presentation, without your name appearing as first author, this would be quite strange.