There is an official announcement on Bitcoincash.org about it.
They said
"If I own Bitcoin, do I automatically own Bitcoin Cash too?
Yes. Because Bitcoin Cash is a fork of the ledger, that means you own the same amount of Bitcoin Cash as you did Bitcoin at the time of the forking block. However, if your Bitcoins are stored by a third party such as an exchange, then you must inquire with them about your cash."
Hope this helps