Ms Sharpe made the announcement at PSNC's May meeting in London, it posted on its website this afternoon (May 9).
She has held the role since 2001, the negotiator pointed out.
PSNC told C+D it could not comment on the reason for Ms Sharpe's departure or who will replace her.
The Twitter reaction
The NPA's reaction
National Pharmacy Association (NPA) chairman Ian Strachan said the organisation was “indebted” to Ms Sharpe for her years of “tireless service” in the sector.
“Sue stands out as someone who knows how to operate within the corridors of Whitehall, yet also understands the pharmacy frontline and cares deeply about what happens to contractors, pharmacy staff and patients,” Mr Strachan said.
"She is an exceptionally capable leader who will be sorely missed," he added.