Executive chairman Roger Jones will return to the role of managing director, which he relinquished to Couling in September 2013.
Jones said the move had been made because of “different priorities” over future plans.
He said: “Over a number of years, in his more recent role as managing director and previously, Robin has made a great contribution to Bath Ales. He leaves with our best wishes for the future.
“To maintain the progress made in recent years and to ensure continuity, I will return to the role of managing director.
'Exciting'
“2014 has been another very good year for Bath Ales with our major achievements met in adding to the number of venues and building the distribution and profile of our core range and Beerd beers. Internally we have also developed both our capability and capacity.
“It is an exciting time for the business and when we considered our future plans there were different priorities, hence the decision taken now.
“Bath Ales is a business in great shape, thanks to the ability and dedication of a great group of people.
“I am excited about what the future holds.”
Couling had worked for Bath Ales in various roles since 2008.