A passenger protection device in which an airbag capable of expanding by receiving a predetermined action signal is disposed on the position of a shoulder belt, and a webbing is wound by means of one winding device, wherein the airbag is folded along a gate-shape guide-form slide guide having high-rigidity parts arranged to have a predetermined distance from one another along one side surface of a low-rigidity part extending in the lengthwise direction of the airbag can smoothly slide along the webbing via the slide guide when the webbing is being pulled out. Moreover, it is possible to fit the folded airbag between the chest and shoulder of a passenger because the slide guide is flexible.