Geoff Couston is leaving JP Corry, where he was group director procurement, to work as a consultant to the timber industry.
Mr Couston, who was with JP Corry for 18 years, said he was looking forward to maintaining his association with friends he had made in the timber sector.
He is also standing down as chairman of the Northern Ireland Timber Trade Association. That role will be taken over by Maurice Brooks, northern region director of the Brooks Group, who will act as chairman until a successor to Mr Couston is found.