Hannover keeper Miller mentally exhausted
The 29-year-old plays for the same club as Germany goalkeeper Robert Enke, who committed suicide in November 2009 by throwing himself in front of a train after battling depression for years.
The club immediately praised Miller for making his case public, describing his attitude as "remarkable."
"I have decided to tell my club, our fans and the media of my illness," Miller told Hannover's website.
"Because of my mental exhaustion, I will immediately allow myself to be treated in hospital."
Miller said he had already been receiving psychological treatment, but decided it was not sufficient.
"Every person, who sets himself out to perform on a daily basis with the highest honour, high motivation combined with high internal pressure, to achieve a result for his team, runs the risk of developing the symptoms of burnout as well and mental and physical exhaustion and further reactions," said psychologist Martin Braun, who has been treating Miller.
"This step is a great demonstration of courage," Hannover club president Martin Kind added.
"His decision deserves the highest respect."
The club did not say how long his treatment would last. Miller joined the club one year ago from Karlsruhe.