In a statement, Mr Bukele said this was in line with his government's position that Venezuelan President Nicolás Maduro was no longer legitimate.
Mr Bukele said the Central American nation regarded opposition leader Juan Guaidó as Venezuela's head of state.
Venezuela has been caught up in a power struggle betwwen Mr Maduro and Mr Guaidó, the National Assembly leader.
Mr Guaidó declared himself interim president in January, claiming that the elections which brought Maduro to power for a second term were fraudulent.
What did El Salvador's president say?
In the statement (in Spanish) posted on Twitter, Mr Bukele said: "The government of El Salvador expels the diplomatic corps from the regime of Nicolás Maduro."
Mr Bukele, who took the presidency in June, said Mr Guaidó was the legitimate leader of Venezuela.
The statement added that in "the near future" El Salvador would receive a new Venezuelan diplomatic corps, named by Mr Guaidó.
What has reaction been?
Mr Maduro has so far made no public comments on the issue.
Meanwhile, the US Ambassador to El Salvador, Ronald Johnson, welcomed the announcement.
In a tweet, Mr Johnson said El Salvador was "on the right side" of the Venezuela crisis.
Mr Guaidó has gained the backing of over 50 countries - but has so far failed to remove Mr Maduro from power.
Mr Maduro is also supported by a number of nations, including Cuba, China and Russia.
Talks between the two sides hosted by Barbados and mediated by Norway recently stalled after President Maduro denounced the opposition for backing the sweeping sanctions imposed by the US.
Venezuela is suffering one of the worst economic crises in history with a quarter of its 30 million population in need of aid, according to the UN.
More than four million Venezuelans have left the country over the past years.
Why is the US involved?
Mr Maduro's government has come under fire by the international community for a number of reasons.
When opposition parties gained a majority in the National Assembly, the president created a rival body stacked with his supporters which assumed many of its powers.
His 2018 re-election was controversial, and labelled as rigged by his critics, after many rivals were barred from running or fled the country.
Protests and demonstrations erupted into violence and were met with a crackdown by authorities which saw civilians killed.
The US has been a frequent target of Mr Maduro's anger.
Mr Maduro has accused the US of trying to kill him, without supplying any evidence. He claims that his opposition is backed by foreign powers, rather than a domestic resistance to his authority.
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