A passenger restraint apparatus 10 in which a seat bag is inflated stepwise includes a seat bag 12 extending in the right-left width direction of a seat and configured to be inflated so as to push a seat cushion from below, an inner bag 13 provided in the seat bag 12, and an inflator 14 that inflates the seat bag 12 and the inner bag 13. The inner bag 13 extends in the right-left width direction of the seat in the seat bag 12, and the inflator 14 is provided in the inner bag 13 so that the longitudinal direction thereof coincides with the longitudinal direction of the inner bag 13. Gas outlets 17 are provided in an upper surface of the inner bag 13. Through the gas outlets 17, gas in the inner bag 13 is discharged upward into the seat bag 12.