The present invention relates to an automatic unbuckling seat belt system adapted to easily buckle and unbuckle the seat belt, wherein the system comprises a seat belt tongue formed with a groove and a seat belt buckle with a latch for suspending in the groove and maintaining the coupled state with the seat belt tongue. An ignition key detecting switch detects whether the ignition key is inserted. An Electronic Control Unit (ECU) controls the latch of the seat belt buckle to be removed from the groove of the seat belt tongue if the ignition key detecting switch detects that the ignition key is taken out. A first relay provides power by being activated according to the control of the ECU. A first electromagnet generates the magnetic force via the power provided through the first relay and pulls the latch from the groove.