Emergency services rushed to the scene in Hammerpond Road after being alerted to the incident just after 5.15pm.
Fire crews used tools to remove a metal grate covering the well and used ropes to lift the man out.
A spokesperson for West Sussex Fire & Rescue Service said: "Joint Fire Control mobilised four fire engines from Crawley, Horsham and Partridge Green to the scene, as well as an aerial ladder platform and heavy rescue tender.
"Upon arrival firefighters found one man in a 15-foot deep well with water inside.
"Crews began the rescue by using tools to remove the metal grate covering the well, and then used a rope system to lift the casualty to safety.
"Once released, the casualty was left in the care of paramedics from South East Coast Ambulance Service."
1. Man rescued from well
Fire crews used tools to remove a metal grate covering the well in a field off Hammerpond Road in Horsham. Photo: Eddie Mitchell Photo: eddie Mitchell
2. Man rescued from well
Firefighters used a rope system to lift the man to safety after he fell into a well in a Horsham field. Photo: Eddie Mitchell Photo: eddie Mitchell
3. Man rescued from well
South East Coast Ambulance Service crews were also on the scene after a man fell into a well in a Horsham field. Photo: Eddie Mitchell Photo: eddie Mitchell
4. Man rescued from well
The well had been covered with a metal grate. Photo: Eddie Mitchell Photo: eddie Mitchell