The 62-year-old Brazilian, initially hired by the co-hosts for two months on a caretaker basis after Frenchman Henri Michel quit at the start of the month, has surpassed expectations with wins over Libya and Senegal.
The government's official website confirmed the contract extension on Saturday and also took the unusual move of publishing his salary, which is $15,000 a month.
Equatorial Guinea, ranked 151st in the world and making their debut at the tournament, lost 1-0 to Zambia in their final Group A match on Sunday, having already made sure of their place in the last eight.
They face Cape Verde, Tunisia and Sierra Leone in their third-round World Cup qualifying group starting in June, although only the first two fixtures will be played during the next year.
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