Students and parents usually spend months preparing for the crucial exam.
The 5.4 magnitude tremor hit the south-eastern port city of Pohang in the afternoon, and dozens of aftershocks have occurred since.
The quake was the second-strongest on record, leaving at least 57 people injured and more than 1,500 homeless.
The annual test, sometimes referred to as "life assignment exam", has been rescheduled for next week for safety reasons.
