He said the time was right for a new challenge after nearly a decade at the helm of the Newsquest-owned title.
Michael, pictured, is to take up a communications role with Public Health England, the government agency charged with improving health and wellbeing and reducing health inequalities.
He said: “The story behind my departure is a simple one – I am ready for a new challenge.
“I have been with The Argus for nearly a decade, the longest I have spent at any of the papers where I have worked.
“The time is right for me to change direction.
“It has been an honour to have had the opportunity to edit the Sussex titles and when I leave later this month I will take with me memories that I am sure will stay for the rest of my life.
“I have been privileged to have worked with some extremely talented people, many of whom are still employed at The Argus today.
“Because of them I am absolutely certain that Newsquest Sussex and The Argus in particular will prosper.
“It has been a real honour to edit a newspaper in the best city in the country and to be welcomed into the heart of that community. As I have discovered during my time here it is a unique city with talent around every corner.
“There is no doubt that businesses such as ours face an incredibly digital future. Decisions taken in recent years have left The Argus ideally placed to take advantage of that.
“Our combined print and digital audience continues to grow. We now have approaching 39,000 people every day reading the paper and just over 40,000 unique visitors connecting with The Argus on line every day.
“We have just recorded a monthly online audience of more than 1,000,000 people.
“We have achieved that through some outstanding work by all the teams who work for us. A significant contribution has also been made by the hundreds of partners we are lucky to work with.
“Editors come and go but one constant is the business they work for. The Argus survives us all. I am proud to have played a very small part in the history of that institution.”
Dawn Sweeney, managing director of Newsquest Sussex added: “I would like to take this opportunity to acknowledge and thank Michael for his considerable contribution to The Argus over the last nine years and thank him for his direction and management of the editorial department.
“I would also like to express my personal thanks to Michael for his commitment and support over the last 15 months and wish him every success for the future. ”