The Seoul Central District Court ruled that Jeon Shik-Ryeol, 44, had violated the national security law which bans South Korean citizens from making unauthorised contact with North Koreans.
Jeon, the head of the traditional Korean dance company "Chool", is a member of the left-wing Unified Progressive Party.
Prosecutors said the dancer met a North Korean spy in Shanghai in March 2011, and sent an encoded oath of loyalty to Pyongyang a month later.
In February, Lee Seok-Ki, a legislator from the same left-wing party as Jeon, was sentenced to 12 years in prison after a rare treason trial saw him convicted of plotting an armed revolt in support of North Korea.