Satoshi Tajiri was the creator of Pokemon, born on August 28, 1965. This make him 47 years old. He is about 9 days away from turning 48. Happy early B-day! xD
The first Pokemon games, Pokemon Red and Green, were released to the public in Feb 27, 1996, so that would make him 30 when the first games came out. It has been about 17 and a half years since then.
I have two sources confirming this that are solely focused on Pokemon info, so I believe I have the right answer. You can also read more about him on these websites too.