The fall happened around 3:26 p.m. at the Northwestern University Allen Center, 2169 Campus Drive, Evanston city officials said.
A 57-year-old man who was operating equipment on the roof fell four stories, officials said. He was pronounced dead at the scene.
The man has not yet been identified.
The Evanston Police Department is working with Northwestern University on the investigation, Evanston city officials said. There were no signs of criminal activity.
No further information was immediately available.