Justice Sarath de Abrew, who had resigned late last year, was found dead in front of his two-storey house in the Colombo suburb of Mount Lavinia, police said.
"The initial report was that he had fallen from the first floor of his house and was pronounced dead on admission to hospital," a local police official told AFP.
The officer said forensic experts were due to visit the scene, which was cordoned off.
There had been several other allegations that he had also sexually abused minors, including one of his own relatives.
He was forced to resign after the influential Bar Association of Sri Lanka urged the chief justice not to allow him on the bench.