An Australian archbishop has become the most senior Catholic cleric in the world to be charged and convicted of covering up child sex abuse.

Magistrate Robert Stone handed down the verdict against the Archbishop of Adelaide Philip Edward Wilson in Newcastle Local Court, north of Sydney, after a magistrate-only trial.

The 67-year-old had pleaded not guilty. He faces a two-year prison sentence.

Wilson is the highest ranking official in South Australia's Catholic Church. The charges alleged that he covered up a priest's sexual abuse of altar boys.

The abuse occurred during the 1970s in the New South Wales Hunter region.

Stone found Wilson guilty of concealing a serious indictable offence of another person between April 22, 2004 and January 7, 2006.