The Englishman walked an average of 20 miles (32 kilometres) a day travelling from the war-batted north of the island and reached a southern village devastated by the 2004 Asian tsunami to complete his eight-day trek.
"Sir Ian Botham crossed the finishing line at the Seenigama Cricket Ground (in the south) today to mark the end of his greatest ever charity walk," his Laureus Sport for Good Foundation said in a statement.
It said he raised more than USD 256,000 for the foundation which funds charitable activities in 34 countries.
"It's all over and it's been terrific," Botham was quoted as saying as he completed his latest adventure. "I am delighted we have raised so much for such a good cause."
On some days, he was driven between towns and he acknowledged in a press conference at the start of his trek that he had revised plans for a longer journey due in part to the sweltering conditions.
"It is considerably shorter than most walks," Botham said. "But, we have to factor something else. It is the heat and humidity. There will be a lot of rehydrating to be done in the evenings."
Botham, who has raised more than USD 20 million for charity with his walks since 1985, has been a frequent visitor to Sri Lanka as a player, television commentator and goodwill ambassador.
The former all-rounder visited soon after the December 2004 Asian tsunami, which killed more than 31,000 people on the island and devastated much of its coastline.
And in March 2011 he visited Sri Lanka's northern region, nearly two years after the end of a decades-long Tamil separatist conflict in which more than 100,000 people were killed.