To provide a seat device that can provide a smooth and stable deployment performance of an airbag.A seat device includes a backrest 1B, an airbag 11, and an upper guide member 41 and a lower guide member 42. The backrest 1B includes a tear line at an upper portion thereof. The airbag 11 is formed of a bag member, in which base cloths are joined to each other, and is provided in an interior of the backrest 1B so that, during inflation, the airbag 11 cleaves the tear line 44 and is deployed to an upper side of the head of an occupant. The upper guide member 41 and the lower guide member 42 are provided in the interior of the backrest 1B so as to guide a deployment direction of the airbag 11 towards the vicinity of the tear line 44 while restricting the deployment direction during the inflation of the airbag 11.