Kim Dong-Chul was sentenced to 10 years in prison with hard labour after a brief trial in the capital Pyongyang. He is the second US national in six weeks to be jailed by Kim Jong-Un's regime.
The 62-year-old, who became a naturalised US citizen in 1987, was arrested in October as he was receiving a USB stick containing nuclear-linked data and other military information from his source, according to state media.
China's official Xinhua news agency reported he carried out "reactionary propaganda" against North Korea "and injected into local people fantasies about the superiority of the United States, in order to shake the stability of the political and social system".
He was paraded in front of reporters in Pyongyang a month ago, when he admitted to stealing military secrets and pleaded for clemency.
Last month, Otto Warmbier, a University of Virginia undergraduate student, was convicted and sentenced in a one-hour trial at the North's Supreme Court, charged with subversion.
Otto Warmbier| Image: Kim Kwang Hyon / AP/Press Association Images
He was jailed for 15 years in prison with hard labour after admitting stealing propaganda material.
The 21-year-old was arrested in early January as he tried to leave the country after visiting as a tourist with a New Year's tour group.
Pyongyang said he had been engaged in anti-state activities during his visit.
North Korea regularly accuses Washington and Seoul of sending spies to overthrow its government.
The US State Department "strongly recommends against all travel" to North Korea and specifically warns of the risk of arrest.
