The France international joined Barcelona from Borussia Dortmund last summer, with the attacker reportedly becoming the world's second-most expensive footballer behind Neymar.
The 20-year-old has struggled to make an impact in Spain, however, with a hamstring injury forcing him to miss a lot of football in the early stages of his Camp Nou career.
Bartomeu has now insisted that Dembele will not be leaving the Spanish giants this summer.
"The option of selling him is not on the table. We are finishing the season and then there will be meetings," Bartomeu told RAC1. "He's an investment for the future. He is very young and we expect a lot from him."
Dembele has managed two goals and seven assists in 20 appearances for Barcelona since his arrival from German football.