Junqueras, in custody since November 2nd, arrived at the Madrid courthouse in a police van to appear before a panel of three judges who will decide whether to keep him in jail or grant bail.
His appearance in court follows snap regional elections in Catalonia on December 21st which saw separatist parties, including a ticket led by his leftist ERC party, retain their parliamentary majority.
A police vehicle transports Junqueras to court on Thursday. Photo: AFP
Madrid had called the poll after Catalan lawmakers declared independence on October 27th, triggering Spain's worst political crisis since democracy was reinstated following the death of dictator Francisco Franco in 1975.
Prime Minister Mariano Rajoy then sacked Catalonia's government, dissolved its parliament and stripped the region of its treasured autonomy.
Catalonia's president at the time, Carles Puigdemont, left for Brussels. He now faces arrest in Spain over charges linked to rebellion, sedition and misuse of public funds while other independence leaders, including Junqueras, are behind Spanish bars pending trial.
Supreme Court judge Pablo Llarena last month refused to grant Junqueras bail, arguing there was a risk that he would repeat the crimes he is investigated for but the former Catalan vice president appealed the ruling.
Junqueras argued before the judges on Thursday that he should be released to be able to take his oath as a regional lawmaker, his lawyer, Andreu Van den Eyden, told reporters.
"What he said was that they free him, that they let him represent the people who voted for him," he said.
Junqueras also reiterated that he favours a "peaceful" path to achieve Catalan independence based on dialogue, he added.
The court is expected to issue its decision in the coming days.
Separatist parties won 70 seats in the 135-seat Catalan parliament, but eight belong to politicians who will not be able to be sworn in either because they are in jail or have fled to Belgium.
They will either have to to secure their release from prison to be sworn in or cede their spot to the next person on their electoral list.