The country's top court rendered its decision on Thursday and, as usual, gave no reason for its ruling.
Jacques Delisle was found guilty in June 2012 of the premeditated murder of his 71-year-old wife, Nicole Rainville.
The former magistrate, who spent nearly a quarter-century on the bench, is believed to be first Canadian judge to stand trial for first-degree murder.
The Quebec Court of Appeal upheld the verdict earlier this year despite Delisle's argument that the trial judge had given the 12 jurors erroneous directives.
His lawyer argued there were procedural errors that led to the guilty verdict, but the appeals court said Delisle failed to show the verdict was unreasonable.
According to its ruling, "the guilty verdict for murder is one that a jury acting judicially could reasonably render" and that "there was sufficient evidence to justify a conviction."
Delisle maintained that his wife, who was paralyzed, was in poor health and took her own life with a revolver that was found next to her.
He claimed to have found the woman dead with a gunshot to the head when he returned to his Quebec city home in November 2009. Police originally accepted that theory until they probed further.
The Crown argued during his month-long trial that Delisle wanted to get rid of his wife to avoid a lengthy divorce and live with his former secretary, with whom he'd been having an affair.
Rainville was handicapped and required constant care. She had been paralyzed on one side by a stroke in 2007 and was recovering from a fractured hip suffered a few months before she died. She was found dead in the couple's condominium on Nov. 12, 2009.
Delisle, who is in his late 70s, retired from the bench in 2009, having served as an appeals court justice since 1992. Previously, he had spent seven years as a Quebec Superior Court justice.