Sata, who heads the Patriotic Front, had 187,863 votes versus 96,325 votes for Banda, election officials announced.
The tally was based on counting in 19 of the country’s 150 constituencies. Africa’s biggest copper producer voted on Thursday to choose a successor to Levy Mwanawasa, who died in August after suffering a stroke.
The country’s largest independent election monitoring group said on Friday the election has been generally peaceful but there were some instances of voting irregularities.
The winner faces the formidable task of matching Mwanawasa’s strong record of fiscal discipline, praised by Western donors, and of cracking down on corruption, two rare successes in Africa.
Banda, a prominent businessman with wide government experience, has campaigned as a steady hand who can keep Mwanawasa’s business-friendly policies going in the world’s 10th largest copper producer.
Sata portrays himself as a champion of the poor.
Although the vote is seen as a test of Zambia’s commitment to multi-party democracy, restored in 1990 after 18 years of one-party rule under Kenneth Kaunda, neither Banda nor Sata is expected to reshape the political landscape dramatically.