Churcher took over the side in August after Steve Larkins' departure and guided the Reds to fifth in National League Division Two South.
"It is with a heavy heart that I have decided not to continue with Redruth RFC for the 2017-18 season," he said.
"I will still play an active role at the club overseeing certain aspects of the coaching side."
Churcher, who is a full-time rugby coach, admitted last week he was considering his future, telling BBC Radio Cornwall: "It's been quite tough this season, especially since Christmas, trying to coach three or four teams in a week.
"I've spread myself quite thin. I've got to look at myself and be a bit selfish about it."
He has since decided to quit as the Reds head coach following the 32-26 defeat by Henley Hawks in the club's final game of the season on Saturday.
"Everyone at the club has been brilliant and I could not have asked for anything more," Churcher told the club's website.
"Currently, Redruth have a real quality group of players, all of whom I have become attached to, which has made my decision to leave even harder.
"All the players have shown so much promise and dedication this season.
"I hope that the memories we have created over the past two years will be the basis for the future on and off the field in continuing to set the standards high and move forward."
Redruth head coach Marek Churcher has decided to step down after eight months in charge.