A side airbag device (100, 100A, 100B, 100C), comprising: an inflator that supplies gas; and a bag-shaped cushion (120, 120A, 120B, 120C, 120D, 120E, 120F, 120H, 120I, 120J) that expands and deploys on a far side of a vehicle seat (104, 110) using the gas from the inflator; wherein the cushion (120, 120A, 120B, 120C, 120D, 120E, 120F, 120H, 120I, 120J) includes: a first chamber (126, 126A, 126B, 126C) that restrains an occupant during expansion and deployment, the first chamber (126, 126A, 126B, 126C) expanding and deploying at a position higher than an upper surface of a console box disposed between the vehicle seat (104, 110) and an adjacent seat positioned on the far side of the vehicle seat (104, 110); and a second chamber (128, 128A, 128B, 128C) connected to the first chamber (126, 126A, 126B, 126C) via a vent hole (142, 142A, 142B, 182, 184, 192, 196, 206, 232), the second chamber (128, 128A, 128B, 128C) being in frictional contact with the upper surface of the console box during expansion and deployment, whereinthe second chamber (128, 128A, 128B, 128C) is provided on a far side on a lower end part of the first chamber (126, 126A, 126B, 126C),, characterized in that the inflator is positioned inside the first chamber (126, 126A, 126B, 126C), wherein the first chamber (126, 126A, 126B, 126C) has a higher internal pressure than the second chamber (128, 128A, 128B, 128C) and caves into the second chamber (128, 128A, 128B, 128C) during expansion and deployment. an inflator that supplies gas; and a bag-shaped cushion (120, 120A, 120B, 120C, 120D, 120E, 120F, 120H, 120I, 120J) that expands and deploys on a far side of a vehicle seat (104, 110) using the gas from the inflator; wherein the cushion (120, 120A, 120B, 120C, 120D, 120E, 120F, 120H, 120I, 120J) includes: a first chamber (126, 126A, 126B, 126C) that restrains an occupant during expansion and deployment, the first chamber (126, 126A, 126B, 126C) expanding and deploying at a position higher than an upper surface of a console box disposed between the vehicle seat (104, 110) and an adjacent seat positioned on the far side of the vehicle seat (104, 110); and a second chamber (128, 128A, 128B, 128C) connected to the first chamber (126, 126A, 126B, 126C) via a vent hole (142, 142A, 142B, 182, 184, 192, 196, 206, 232), the second chamber (128, 128A, 128B, 128C) being in frictional contact with the upper surface of the console box during expansion and deployment, whereinthe second chamber (128, 128A, 128B, 128C) is provided on a far side on a lower end part of the first chamber (126, 126A, 126B, 126C),, characterized in that the inflator is positioned inside the first chamber (126, 126A, 126B, 126C), wherein the first chamber (126, 126A, 126B, 126C) has a higher internal pressure than the second chamber (128, 128A, 128B, 128C) and caves into the second chamber (128, 128A, 128B, 128C) during expansion and deployment. a first chamber (126, 126A, 126B, 126C) that restrains an occupant during expansion and deployment, the first chamber (126, 126A, 126B, 126C) expanding and deploying at a position higher than an upper surface of a console box disposed between the vehicle seat (104, 110) and an adjacent seat positioned on the far side of the vehicle seat (104, 110); and a second chamber (128, 128A, 128B, 128C) connected to the first chamber (126, 126A, 126B, 126C) via a vent hole (142, 142A, 142B, 182, 184, 192, 196, 206, 232), the second chamber (128, 128A, 128B, 128C) being in frictional contact with the upper surface of the console box during expansion and deployment, whereinthe second chamber (128, 128A, 128B, 128C) is provided on a far side on a lower end part of the first chamber (126, 126A, 126B, 126C),, characterized in that the inflator is positioned inside the first chamber (126, 126A, 126B, 126C), wherein the first chamber (126, 126A, 126B, 126C) has a higher internal pressure than the second chamber (128, 128A, 128B, 128C) and caves into the second chamber (128, 128A, 128B, 128C) during expansion and deployment.