Dave Picton, chairman of the mill trust, said, "This is a tremendous boost for the windmill.
"It would have taken us ten years to raise the money we need to make the mill more attractive and accessible to visitors."
The grant will enable the mill's roundel, at the base of the building, to be fully carpeted and insulated and access will be improved for people with disabilities.
It will provide a much-needed centre for the mill's collection of photographs, models and agricultural implements and offer a venue for school children and students to learn about industrial history, science and engineering. It is hoped that EDF Energy will provide a new exhibit at Stone Cross about the importance of wind power today.
At present the Stone Cross Windmill is only open on Sundays and Bank Holidays from April to September but the grant will enable the trust to open the heritage centre by appointment all year round, even when the mill is undergoing winter maintenance.
Councillor Pam Doodes, leader of Wealden District Council and a board member of the WARR Partnership, said, "We have such a rich heritage in Wealden and, in the Stone Cross Windmill, we have a great example of sustainable technology from the 1870s. European Leader funding is helping improve the quality of our local attractions, encouraging more visitors."
So far this year the Wealden and Rother Rural Partnership (WARR) has awarded £101,369 to help Wealden's rural businesses
Individual projects are eligible for grants of up to £50,000. For more information visit www.wealden.gov.uk/LEADER or call Kathy Fordham on 07985 871792 or the WARR Partnership team on 01424 787400.