The publisher of J.K. Rowling's books varies depending on the region. However, the
primary publisher for most of her works, including the Harry Potter series, is
Bloomsbury Publishing. They published the first Harry Potter book in the UK and have continued to be her primary publisher there.
In the United States, Scholastic is the publisher of her books.
Other publishers handle her books in different parts of the world, so depending on where you are located, you might see a different name on the book's cover.