Spain's Foreign Minister Jose Manuel Alvarez said Mr Gonzalez left the country on a Spanish air force plane at his own request.
He added that the Spanish government defends the political rights of all Venezuelans.
Venezuela has been in a political crisis since authorities declared President Maduro the winner of the July 28 election.
The opposition claims it has evidence that Mr Gonzalez won by a comfortable margin, and has uploaded detailed vote counts online showing that Mr Gonzalez defeated Mr Maduro by a landslide.
Many countries, including the United States, the European Union and several Latin American countries, have refused to recognize Maduro as the winner unless Caracas releases detailed voting data.
Mr. Gonzalez had been in hiding for a month before leaving the country, ignoring three summonses to appear before prosecutors.
Post-election violence in Venezuela has left 27 people dead and 192 injured, and the government says it has arrested about 2,400 people.
