Hi junnan,
All I can say is that, ANU (in my opinion) is the number one in the list if you want to study econ in Australia. It is included in the group of eight, a group of academically dedicated australian universities, perhaps similar to Russel Group in the UK. The school, CBE, has been known as the best in the continent. Even in any websites, they rank higher. So you might not to worry. My life has been surrounded by people from ANU these past years. Mostly because of my lecturers, superordinat co-workers, and then finally jump to my close friends. Maybe also because of the diplomatic relationship between my country and Australia so it is not hard for me to find people graduated from there, and frankly, they are always ended in a post where having significant role to the country's development. I think they are the best in general, but if you are focused on development econ, then you are on the track, I guess.
Good luck!