Shane Hobbs, of Dawlish Warren, Devon, was jailed for 16 months after admitting sexual assault on one woman and common assault on a second during the incident in February, this year.
Hobbs, 26, was captured on CCTV laughing as he walked away from his shocked victim after thrusting his fist down her trousers.
Cameras followed Hobbs as he staggered through Exeter city centre lunging and fondling several women enjoying a night out, the court heard.
The attack on the Chinese student from Exeter University left her too frightened to go out at night, Exeter Crown Court was told.