A passenger constraining apparatus configured to limit the amount of upward inflation of a seat bag is provided. A passenger constraining apparatus 10 includes a seat bag 12 extending in the lateral width direction of a seat, and being inflatable so as to push a seat cushion from below, a retainer 11 installed on a seat pan 1, an inner bag 13 arranged in the seat bag 12, and an inflator 14 for inflating the seat bag 12 and the inner bag 13. The inner bag 13 is connected at the lower portion thereof with the retainer 11, and the upper portion thereof is connected to the upper portion of the seat bag 12.