Tony Dench had been in the role for five years.
No reason has been given for his departure. But in a statement, Dench said he had achieved his objectives at the network.
“When I joined SHARE five years ago, the SHARE board asked me to grow the business and to prepare it for the upcoming licensing regime.
“I believe that I can justifiably say that, together, we have achieved both of those goals.
“The full FAP licences are in place for what is now three businesses, and SHARE has trebled in size on a number of measures during that time.”
SHARE chairman Richard Thomas, was sorry at his departure.
“We have been delighted to have Tony at the helm of our team and, while we respect his decision, we are genuinely sad to see him go,” he said.
It is not clear exactly what Dench will do now, but the statement from the company said he would continue his career in roles at director and executive level within the wider financial services sector.
SHARE and Newpark make up one of the largest networks of mortgage, financial and insurance advisers in the country.
Dench will remain as CEO to help ease the transition to new management.
He is also a shareholder in the company.
Originally from Belfast, Dench worked for the Bank of Ireland before migrating here in 2005.