MacFarlane, who returns to the UK following a spell in Belgium as global director of customer standards, was in charge of the company's off-trade division between 2004 and 2006.
He joined the business in 1992 and has also worked as the company's general manager in Ireland, as director of customer marketing, and as director of marketing for Stella Artois.
Evans is leaving InBev after 14 years with the company.
"It has been a privilege to lead the UK business over the
past two years and I've thoroughly enjoyed my time with InBev," he said.
"However, the time is right for me to move on and seek new challenges. I know Stuart well, he is a great guy, and I wish him and the team every success in the future."