An external airbag device is provided which can smoothly deploy its airbag with being caught by neither a rear edge of a hood nor a windshield wiper. A lid 8 is allowed to be displaced relative to a retainer 2 in the vertical direction because hooks 10 are movable in the vertical direction within apertures 16. When an airbag 4 is inflated, the lid 8 is lifted and is torn to open outwardly by the inflation pressure of the airbag 4 to create flaps 28, 30. The flap 28 which pivoted outwardly toward the front of the motor vehicle is laid on an outer surface of a rear edge portion of a hood 18. The flap 30 which pivoted outwardly toward the rear of the motor vehicle is laid on a cowl top 22 below the windshield 20 to cover windshield wipers 26.