An airbag device for front passenger's seat of the present invention includes an airbag folded and housed in a case. A rear side face of the airbag as completely deployed confronts an occupant and serves as a restraint face. The airbag includes an upper inflatable portion and a lower inflatable portion arranged vertically at airbag inflation. Rear side faces of each of the upper and lower inflatable portions define upper part and lower part of the restraint face. A lower wall of the upper inflatable portion and a top wall of the lower inflatable portion contact and overlap with each other as the airbag is completely inflated, and contacting face of the top wall and the lower wall is wide enough to stay contacted even when either the upper inflatable portion or the lower inflatable portion restrains a part of occupant.