Who is the best selling author of childrens book?

The best-selling children's author is R. L. Stine with over 400 million books sold according to very recent sources. He beats J. K. Rowling and Dr. Seuss in sales.

However, you must take into account. R.L. Stine has over 160 books of the goosebumps and other books as well. Whereas, J.K Rowling has only 7 novels, her books have sold more than 400 million copies worldwide. And she is the only self-made billion dollar author in history.