In an inflated and deployed state of a side-airbag, a shoulder bag section is disposed to extend from the side of a shoulder of a seated occupant toward the vehicle front side, above a main bag section. The vehicle width direction dimension of the shoulder bag section is set smaller than that of the main bag section, and a vehicle width direction inner side face at an upper end side of the main bag section slopes or curves so as to rise on progression toward the vehicle width direction outer side. An upper arm is pushed upward by making sliding contact with this face. Moreover, the shoulder can be restrained by the shoulder bag section, even when the seated occupant moves under inertia obliquely toward the vehicle front.