Mr Anwar is being tried over allegations that the 63-year-old father-of-six sodomised a 25-year-old former aide at an upmarket condominium in June 2008.
"I find a prima facie case... has been made out against the accused," High Court judge Zabidin Mohamed Diah told a packed courtroom.
"Therefore the accused is called to enter his defence."
"I found (prosecution witness Mohamad Saiful Bukhari) to be a credible witness. There is nothing improbable about his evidence. His evidence is reliable," he said.
The judge also found there was evidence that Mr Anwar and Mr Saiful were at the scene of the alleged crime at the time in question and that there was "opportunity for the offence to have taken place".
Sodomy is illegal in Muslim-majority Malaysia, whether or not between consenting adults.
Mr Anwar insists the accusations are part of a long-running government plot to derail his political career, but authorities deny any conspiracy.
Mr Anwar's original 1998 sodomy conviction was later overturned and he was freed after serving six years in jail, becoming an electoral threat to the ruling Barisan Nasional, which has been in power for half a century.
The trial is to resume on June 6, according to court officials.
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