"It's been 16 years of 70-odd hour weeks back-to-back and not much downtime," he said. "I want to spend some more time with my kids."
APN said Bradley had led the company to a profitable, market-leading position, and would stay involved with GrabOne as an adviser after he stepped down from the top role.
Vaughan Magnusson, who has been chief financial officer and a key member of the daily deal firm's leadership team since its launch, will take over as chief executive.
Bradley said he was most proud of building the team of 130 staff that operates the business today, as well as fending off competition and retaining GrabOne's market-dominating position.
"For a group buying business I think we're up there with the world's best.
"I certainly think we're the best in Australasia by a long margin in terms of customer satisfaction and the sort of revenue we do," he said.
"That's all down to the quality of the staff."
GrabOne New Zealand posted earnings before interest and tax (ebitda) of A$1.2 million in the six months to June 30, 2012, and that figure was expected to double in the second half of APN's financial year.
APN reports its full-year result on February 21.