Over the next few months Nationwide said it will search for a successor to Beale, who has been its chief executive since 2007 – successfully guiding the bank through the financial crisis.
In the financial year to April 2015 the bank increased its statutory profits by 54% and its underlying profits by 32% to £1.04bn to £1.216bn respectively.
Beale said: “This is one of the strongest sets of results we have ever announced, demonstrating that, yet again, it is possible to build a successful business by doing the right thing.
“We have reached a level of profitability that will allow us to continue to invest in our business to improve our members’ experience and also to strengthen our balance sheet.
“This makes Nationwide one of the safest places on the high street for our members’ money.”
He added: “Succession of leadership is best dealt with from a position of strength and hence the time has come for the society to identify and appoint its next chief executive.”
Nationwide said it has now become the second largest mortgage provider with a market share of 31.2%, despite seeing net and gross mortgage lending fall year-on-year.
Gross lending was £27.1bn in 2014/15, a reduction from £28.1bn the year before, while net lending reached £7.1bn, less than the £9.9bn recorded the year before.
The bank's lending to first-time buyers also fell from 58,100 in the last financial year to 46,000 in the year to April 2015.
Geoffrey Howe, Nationwide chairman, said: “I would like to thank Graham for his enormous contribution to the success of this organisation.
“He has led the society safely through the worst financial crisis in living memory and at the same time created a truly modern mutual, with the needs of our members at the forefront of all that we do.
“He has also positioned the organisation for a digital world – ready to embrace the future and continue to innovate for the benefit of our members.
“This is the right time to plan for the future and in the meantime Graham will continue to lead the society and will remain, as always, focused on the job in hand.”