© ReutersCongolese president Joseph Kabila has rejected claims of corruption in the recent national elections.
The court's president, Jerome Kitoko, said Mr Kabila had won 48.95 per cent of the vote.
"In consequence, Joseph Kabila is proclaimed president-elect of the republic with a simple majority," he said at the justice ministry.
The court said the opposition had failed to provide proof of their allegations.
Congo's election commission last Friday declared Mr Kabila winner of the vote which observers said lacked credibility and was marred by irregularities and violence.
The opposition reacted immediately to the court's decision saying they "totally rejected" the ruling.
"The supreme court is just an instrument of Mr Kabila, just like the electoral commission," said Alexis Mutanda, campaign president of veteran opposition leader Etienne Tshisekedi.
Mr Tshisekedi, who came second in the vote, has called the election results "a provocation" and said he considered himself Congo's new president.
"The party is going to decide what to do, we just think it's a masquerade," Mr Mutanda said by phone.
The Congolese people are waiting for Mr Tshisekedi to call for protests but could take matters into their own hands, he added.
Mr Kabila has brushed off criticism of the vote while the head of the election commission has said any irregularities during the poll were not enough to have changed the outcome.
Norbert Mitumba Kilombo, Kabila's representative at the court, said after the judge's decision it was a happy day for Kabila and the country.
"I'm joyful to see that despite the difficulties, this period of the presidential election is coming to a happy conclusion," he said.
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