Occupant protecting device in vehicle seat

In order to provide an occupant protecting device in which a bag placed at the front of a seat cushion is inflated to locally and sufficiently push up or sufficiently harden the front of the seat cushion in order to prevent the forward movement of the waist of an occupant, an inflatable tube (20) is placed under the front of a cushion pad. Gas is introduced from an inflator (34) into the tube (20). A plate (50) is provided to hang over the tube (20). The plate (50) is pushed up when the tube (20) is inflated. The plate (50) tapers toward the top.