The incident happened yesterday (Wednesday) at around 1pm.
CCTV images show a young man with a black Nike hoodie, joggers and trainers who stole the bike (a green and black Giant mountain bike) and made off towards Valley Road.
The college said the bike is the student's only way to get to school and work.
Police have been informed and are currently investigating.
Anyone with any information should call 101 and quote reference number 12180226480.