The 41-year-old actor will make his debut as Batman in Dawn of Justice in 2016. He was spotted looking particularly buff over the weekend as he ran errands in Los Angeles.
Affleck began a rigorous exercise and diet regime earlier this year in order to prepare for the role. He reportedly works out five or six days a week for three or four hours, and consumes 5,000 calories a day.
"I'll tell you that there is a man working out at my house right now -- I'm sure -- for his second time today," wife Jennifer Garner said in April. "And he has 17-inch biceps."
Batman v Superman: Dawn of Justice is scheduled for release May 16, 2016. The movie stars Henry Cavill as Superman, Gal Gadot as Wonder Woman and Amy Adams as Lois Lane.