The Wineworld London board, owners of Vinopolis, confirmed Ellwood will be leaving the company to pursue other interests and is retiring from the board with effect from 23 July.
Ellwood's successor will be announced in due course.
Wineworld London chairman Sandy Anderson said: "In his time as the managing director, Rupert has attracted corporate business from the likes of Sony Ericsson. He has also overseen the granting of planning permission for our future development plans. On behalf of shareholders, I would like to thank Rupert for his hard work and dedication."
Ellwood said: "I'm extremely proud to have served the Vinopolis Board and to have achieved such success in making Vinopolis the fun and engaging corporate events space it is today. I feel that this is the right time to leave for my next career move."
Ellwood will join Waitrose's international development team on 30 August as manager of international growth. His new role will be to develop new customers and routes to market for Waitrose in overseas markets.