The Hollywood star entered the Betty Ford Centre three weeks ago but is due to leave later today, the website added.
Butler entered into rehab in the hopes of avoiding addiction to prescription drugs, it is reported, having thought he was becoming over-reliant on prescription drugs.
The actor apparently had problems with pain after the physically demanding shoot for 300 in 2006. He is said to have exacerbated the problem with a surfing accident in December while filming Of Men and Mavericks.
The film is based on the life of US surfer Jay Moriarity. Butler plays Rick ‘Frosty’ Hesson, Moriarity’s mentor.
Butler, who is a teetotal, has also spoken about issues with alcohol in the past.
He said: “I used to drink until I couldn’t remember anything. I was just mad for it and on a death wish. It was madness.
“One or two drinks was never enough for me. I was a foot-on-the-floor-all-the-way drinker, so it had to go. I don’t miss it.”