Yes it absolutely exists. I have lived there.
This can't be serious right? What kind of an ignorant question is this?
I have been to Australia and lived there for about a year. Yes Kangaroos do exist. I have seen, touched, and fed them at the petting zoo. I don't even know why I'm spending time arguing this topic.
If you don't believe if Australia exists, why don't you buy a plane ticket and visit the place.
Visit the local zoos and see the kangaroos for yourself.