He told staff of his plans on Friday, and will leave the paper at the end of September. He will be 60 later this year.
Graham has worked for Northcliffe Newspapers for the past 18 years, and has edited the Evening Post since the group bought the paper 12 years ago.
During his time there he has led a number of high-profile campaigns, notably against replica guns, for controls on fireworks, and against secrecy by local authorities.
The paper has won numerous awards including Newspaper of the Year and Campaigning Newspaper of the Year as well as trophies from the Plain English Campaign, the Race in the Media organisers, and for championing consumer issues.
Under his leadership the paper has also been a talent factory, with three current Northcliffe editors previously working as Graham’s deputy.
Derby Evening Telegraph editor Steve Hall worked alongside him before becoming editor of the Express and Echo in Exeter, Jon Grubb was deputy editor at Nottingham before being appointed editor at the Scunthorpe Telegraph and then the Lincolnshire Echo, and Marc Astley was the No2 at Nottingham before becoming editor of the Express and Echo.
Five current deputy editors on major regional titles also developed their skills on the Evening Post during that time and a range of journalists have gone on from Nottingham to national titles or to the Parliamentary Lobby.
Graham told HoldtheFrontPage: “Editing Nottingham has been a privilege. I can think of no better job apart possibly from that of Tiger Woods!
“But I want time to do things that my current role precludes.
“The Evening Post has a great editorial team and it has been very rewarding to work with so many excellent people.”
He began his career at the Daily Express in Scotland and worked at Aberdeen Journals.
He also took a break from newspapers from 1973 to 1979, when he set up and ran his own restaurant.