Soltani, a member of the Center of Human Rights Defenders founded by Nobel Peace Prize Laureate Shirin Ebadi, was arrested last year on charges of revealing state secrets and harming Iran's national security.
Human rights groups said Soltani's arrest was politically motivated and designed to discourage others from pursuing sensitive human rights cases.
Soltani represented the family of Iranian-Canadian photographer Zahra Kazemi, who died while in government custody. He also represented Iran's highest-profile political prisoner, journalist Akbar Ganji.
The court originally set a bail of $800,000 to free Soltani but lowered it to $100,000 following protests from his lawyer.
(compiled with agency reports)