A judge at the Supreme Court in Madrid on Thursday had ordered Carme Forcadell to be held on charges of "rebellion" -- which carries a maximum jail term of 30 years -- as Spain's worst political crisis in a generation rumbles on.
Forcadell was one of several dismissed Catalan officials to be detained after their shock decision last month to declare the region of 7.5 million people independent from Spain.
A court spokeswoman said Friday that the 150,000-euro bond had been paid.
"Returning home... with the calm confidence of having acted correctly," Forcadell posted on Twitter after her release.
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The Catalan crisis has caused shock waves across the European Union (EU), prompting nearly 2,400 businesses to move their legal headquarters and re-register outside of the wealthy northeastern region.
Lawmakers opted to split from Spain, claiming they had a mandate after a referendum on October 1 in which 90 percent of voters backed secession.
After the declaration, Madrid dismissed Catalonia's government, dissolved parliament, suspended the region's autonomy and called new elections for the region next month.
Forcadell appeared at the Supreme Court in Madrid on Thursday along with five former Catalan lawmakers.
She left in a police car, but the others were given a temporary reprieve by the judge, who said they must pay 25,000 euros each within a week or be detained.
"The declaration that they won't do anything against the constitutional order sounds good to me," said Spanish government spokesman Inigo Mendez de Vigo. "We're helping Catalonia return to normal."
Writing on Twitter, deposed Catalan president Carles Puigdemont, who has left for Belgium, said Forcadell had "to sleep in jail for having allowed a democratic debate."
Puigdemont and four former Catalan ministers are due to appear before a Belgian judge next week after Spain issued an EU-wide warrant for their extradition.
Puigdemont, a 54-year-old former journalist, says he will not get a fair trial in Madrid, and has called on authorities to release Catalan "political prisoners".
Forcadell, a lifelong advocate of Catalan independence, has said that as parliamentary speaker she did not have the power to stop the October 27 vote in which lawmakers backed a break from Madrid.
Prime Minister Mariano Rajoy has urged voters to turn out en masse for the December 21 elections in Catalonia, a region that accounts for a fifth of Spain's GDP.