Stork, 21, joined Sunweb in 2017. Last season, he wore the leader's jersey for one stage in the Tour Alsace and finished fifth overall.
After two years of "invaluable value" for the Development team, Stork impressed management at the recent WorldTour training camps, said team coach Sebastian Deckert. "We are convinced that the he is ready to take the next step with the WorldTour program."
Stork called it a "childhood dream come true", and said that the Sunweb developmental program "really is among the best in the world."
He will make his WorldTour team debut the end of March at Coppi Bartali.
The German is the fourth rider to move up from the Development Team this year, joining U23 world champion Marc Hirschi, U23 German champion Max Kanter and former U23 cyclocross world champion Joris Nieuwenhuis.