The land and building earlier housed Asha Central Hospital, but is now being used Sri Lanka's military as a hospital.
John Keells Stockbrokers said in a stock exchange filing that Actis Investment Holdings SL Ltd, had bought the stake at 250 rupees a share.
Actis is an emerging market private equity group formerly known as Commonwealth Development Corporation (CDC) a fund set by Britain.
The shares were sold by Softlogic Holdings and Dai-Nishi Securities a unit of Soflogic Holdings.
In another deal, valued at 607 million rupees, 81 million shares of Asiri Hospital Holdings (a 9.1 percent stake) was bought by Solftlogic Holdings for 7.50 rupees.
The seller was Asiri Hospital Holdings - Employee Share Trust.