A bank surveillance camera took pictures of the suspect at the Jewel grocery store at 3570 N. Elston about 8 p.m. Saturday.
He was described as a white man, between 40 and 50 years old and about 6 feet tall.
Chicago police said the robber handed a bank employee a note demanding money.
After getting an undisclosed amount of cash, the robber left.
No one was hurt.