The Argentina international, whose current deal expires in the summer of 2018, has yet to agree new terms, sparking speculation he could leave the Catalan club.
Bartomeu, however, is confident the 29-year-old will remain at the Nou Camp.
Bartomeu said: "I believe we've got a team with incredible players, all of them.
"There is nonetheless a leader of course, Leo Messi, he is well known and popular all over the world.
"We're all convinced, we're all positive Leo Messi will end his sporting career in Barca.
"All the members of Barca believe this is how it has to be, because he is the player that in the last few years has brought us sporting success."