Angela Morrison is currently European strategy director at Asda, prior to which she was its IT director.
Miller has headed the IT unit at Sainsbury for more than four years, during which time most of the core systems were replatformed.
A Sainsbury spokeswoman said: “We have achieved significant improvements in reliability and reduction in operating costs. Moving forward, our focus will be on exploiting the capability of our systems, continuing to improve reliability and reducing overall IT costs.
“Maggie will stay on until March 2005 to help ensure a smooth handover.”
Sainsbury admitted in October that its IT overhaul had not delivered, with £140m in systems being written off and others being simplified or put on ice.
The retailer has also renegotiated its contract with consultants Accenture and announced plans to rebuild its in-house IT team.