OCCUPANT PROTECTION DEVICE

An occupant protection device is such that an airbag is housed in a housing region of a lap belt portion that can be disposed on a front side of a waist portion of an occupant seated in a seat. The airbag can receive and protect an upper body of the occupant using a rear face side occupant restraining face when inflation is completed. The airbag includes an exhaust port that can discharge an inflating gas and a regulating valve mechanism that restricts a discharge of the inflating gas from the exhaust port. The regulating valve mechanism permits a discharge of the inflating gas from the exhaust port when a protrusion upward of the airbag from the housing portion is restricted, and restricts a discharge of the inflating gas from the exhaust port when a protrusion upward of the airbag from the housing portion is not restricted.