Abstract: An automatic guard device for seatbelts in a car comprises two clasps, two elastic switches, two contact switches and a warning main unit. Each elastic switch is disposed in each clasp and connects with each contact switch by way of an AV wire. The contact switches are disposed in front of the seatbacks of the driver's and the front passenger seats respectively. Each elastic switch connects with a corresponding AV terminal on the main unit. The main unit is provided with dual circuits therein connecting with the power source of the car via the lighter socket in the car. When one of the contact switches is touched, the main unit emits a warning sound and/or flashes to remind the driver and the passenger at the front seats in the car that their seatbelts have to be fastened. Once each elastic switch is pressingly contacted by the lock piece on each seat belt, the buzzer and/or the light emitting diodes in the dual circuits ceases emitting the warning sound and/or the flashes.