Malcolm Hayday, chief executive and one of the founders of Charity Bank, will step down from the post this year.
Hayday has not revealed what he plans to do next but has agreed to remain at the bank, which finances charities, social enterprises and community organisations, until a successor is found.
He said in a statement: "After 19 years of establishing and growing the Charity Bank model to the point of profitability, I believe now is the right time for me and the right time for Charity Bank, to hand over the reins to a successor who can take the bank to new heights."
He said the bank had developed "a unique banking model that responds to real social needs by financing charities and social enterprises".
A bank spokeswoman said: "Malcolm is 62 and feels he has one project left in him but he doesn’t want to give any details yet."
Hayday joined Charities Aid Foundation in 1993 to explore the idea of loan finance for charities.
He started Investors in Society, a pilot loan fund, in 1995 before overseeing its formal incorporation as Charity Bank in 2002.
Charity Bank’s balance sheet was £6.4m in its first year. It now exceeds £80m and expects to report a surplus of more than £350,000 this year.
George Blunden, chair of Charity Bank, said in a statement that Hayday had "secured his place in the history of social finance" and left a "thriving organisation".
Blunden added: "His dogged determination to realise the vision of a bank from and for the charity sector has brought about change in the way charities are financed. That change is now gathering speed."
The bank has begun the process of recruiting a successor.